Never ridden one, but from a friend who does regularly:
1 - It’s not a matter of if you fall but when.
2 - Only have 1 or at most 2 keys on your motorcycle keyring, no big dangling of keys off of the ignition switch, this is some sort of expected motorcyclist protocol of acceptance and community bonding, not anything practical.
When I was a kid, a cheap ring came open while I was on my Honda 50, and I left keys between home and my Grandmother’s house. 
Get a copy of Proficient Motorcycling: The Ultimate Guide to Riding Well, and read it over and over. It’s a good read and has a lot of good information in it.
Get a white helmet, not a black one. Yeah, black (or blue, or red) ones look cool, but white ones are much more noticeable and that is the key. You want to be sure others notice you (not just see you).
Don’t fall for the “It’s not if you go down, but when” stuff. It’s a fatalist attitude and is not even true. What is true is “If you go down, it’s gonna hurt”.
Don’t depend on “loud pipes save lives”. My problem with this is it attempts to make others (the ones who are startled by the loud exhaust) be responsible for your safety. Only you are going to be responsible for your safety.
Remember that the majority of motorcycle accidents involve riders with less than two years experience. After you have ridden for two years, remind yourself than nearly as many accidents involve riders with more than two years experience.
Contrary to popular belief, riding on the interstate is much safer than on surface roads. Nobody on the interstate is going to pull out 90 degrees to your direction of travel. Sure, the drivers on the superslab will often change lanes without looking, but that is rarely fatal. On the surface roads, they will pull out right in front of you, which often is fatal.
This is has a practical origin. A large, dangley ring of keys will tend to scratch up all the surfaces around it. Motorcyclists often pamper their babies and want to keep them nice. Also, years back anyway, it wasn’t unknown for the weight of a large ring of keys to cause problems with the ignition system. It’s happened with cars, too.
Remember, a wet street is a very slippery street. A very slippery street.
Regarding people at intersections crossing in front of you - treat unregulated intersections the same way you would a “stale” green traffic signal. Prepare yourself to stop (or evade the idiot) for the entire approach. Always assume they WILL pull out in front of you and know what you are going to do in response.
Also, use their wheels as your visual reference. It is much easier to detect a small rotational movement of the wheel than the linear movement of the whole car. The same applies with unexpected lane changes. It’s much easier to detect the shrinking space between their wheels and the lane marker than noticing the whole vehicle getting closer.
If you’re just starting out, and you don’t have fun on a 250, you’re doing it wrong. Those things have plenty of power for everyday riding, and you won’t feel any lack of power because you won’t have any thing to compare it to, experience wise. I still have fond memories of my old Honda 90. It was all the fun of riding a bicycle, without the exertion. Imagine a cool Fall morning, floating down a tree lined secondary highway, taking in the colors and smells without the windows and roof of a car blocking the view. You’re gonna love it!
it depends on what 250. a 40 hp Ninja 250 is going to be a very different beast from a 19 hp V-Star 250.
OP, as to gear, I found that Olympia Moto Sports made jackets I liked the most. I also had a few by Rev’it, but found the Olympia to just do more for far less money.
I also have a Shoei head, so have gravitated to their helmets. Definitely find a shop with a lot of brands and try each. They really do fit differently.
Already some great info above. I’ll add a couple more for now.
Always be looking up and ahead (you want to have the horizon in-sight). The MSF instructors will be reminding you all weekend. It’s probably the best and most-valuable skill a rider can have.
Another way to say that is, don’t look at the ground in front of the front wheel. This is the mistake I see almost every new rider/student making. It’s also one of the hardest skills to master but you’ll be a better rider once you do. You’ve got to be looking and planning ~10 seconds ahead. Your brain needs time to process the enormous amount of information presented to you, especially when riding in traffic. You want to maximize your available perception, response, and reaction times.
Secondly (this isn’t part of the course), ride like there’s no one in those cars. No need for personalities to get in the way. No one’s out to kill you, they just don’t see/expect you. Also, since there is no driver in any car, you can drop any expectations you may have that they’re going to follow the rules. You should expect any vehicle to do anything at any time. Sure, that’s a little bit of a stretch because most vehicles do follow the rules. But treat those *rules *as general guidelines, not guarantees. Another reason to imagine there’s no one in the cars is that no one need be at-fault. You are solely responsible for your safety. Sure, that car/truck may have made a maneuver that was illegal and wrong, but don’t waste time on apparent justice. Instead use those resources to manage and avoid the situation to stay upright and uninjured.
Also… get out in the dirt (with a suitable bike) where you can slide around and fall down a few times. That will do wonders for your education and enjoyment!
Are you at all interested in riding on dirt? If I had to do it over again, I think a 250 dual sport bike would be a good a first bike (assuming one has the inseam for it.) The newer ones will do anything a new rider needs them to on-road (and are forgiving of being dropped, which is nice) but once you move on to a different street bike it’s still nice to have something that’s nimble for messing around in the hills.
That said, I have a Ninja 250 and it’s a really great bike. It actually wasn’t my first bike; I sort of inherited it from someone and mostly use it as a runabout, but I’ve also done longer trips on it. Unlike a lot of other starter bikes out there, it’s a pretty nice basic utilitarian bike you’re only really going to outgrow when you decide you want something more specialized.
One slightly cautious note with them is that the dual carburetor set up on them is kind of fiddly by modern motorcycle standards. If they don’t get somewhat regular valve adjustments and carb syncs they run like crap, especially cold. Problems with the idle circuit from being left with old gas are also somewhat common. None of that’s unfixable, particularly if you’re handy, but if you are looking at one the ideal thing is to have the seller not warm the bike up ahead of time. Of course getting a newer one with fuel injection would eliminate that problem, and yes, ABS is definitely something you want if you can get it. Also, the Honda and Suzuki 250/300 sport bikes I think are pretty fungible with the Ninja although at least around here there’s vastly more Ninjas on the used market.
Get a jacket with reflective patches or that’s light colored, in addition to a white or reflective helmet.
Also, my husband and I had to drive a long distance on a rural highway recently, and there were a bunch of motorcyclists weaving in and out of traffic, which looked very unsafe. Please don’t do this.
Pick which leg you like best? (…not that it’ll ever come up…) 
**What advice do you have for a new motorcycle rider?
**
Sell it and get a car.
I was pleasantly surprised that I could pick up my 750 lb bike (Triumph Thunderbird) when I tipped it over in a parking lot. It’s all about where the center of gravity is, apparently.
Speaking of which: most bike damage happens in parking lot tip-overs. Get very comfortable with low speed maneuvering in tight spaces. (I wish I was better at it.) I took an all-day course where we basically did little more than U-turns; it was worth it.
But to reiterate what others have said: ATGATT. Don’t be a squid. Assume that you’re invisible, and the only people who can see you are trying to kill you. Do not linger in the blind spots of cagers; stay out of the blind spot, then zip through it as you pass (it’s fun!)
Keep your head up on turns, looking at your line and your exit out of the turn. Don’t fall into Target Fixation Syndrome (aka “See It - Hit It”).
Besides the obliviousness of car drivers, you have to remember that you’re expected to adhere to the same rules of the road as everyone else. It’s the law, and a lot of people get hurt when they do things car drivers don’t expect them to. Don’t lane split. Don’t illegally pass on the right either, even if you think you’ll get by drivers stopped at a light quicker - if one of them opens a door, you’re not getting anywhere quickly. Stop at every red light instead of blowing through any of them them (that one gets you hit by drivers turning whose right of way you just unexpectedly violated). Make sure you leave plenty of room when you pass a car, especially when you’re new at it and your perceptions aren’t well developed yet. And even if you’re in NH, wear a goddamn helmet.
Where are you taking the course?
- See a lawyer and make sure you have a valid up-to-date will.
- See an insurance agent and make sure you have as much life insurance as you can afford.
- Also get the best hospital coverage for accident insurance.
- Tell all the people you love how you feel about them and kiss them goodbye - just in case.
Many people have told you that automobile drivers will actively try to kill you. The truth is that they may not want to kill you. But the effect is the same. The people who told you this are not fooling.
I rode a Honda 750 and thought it was a very shitty bike. People raved how wonderful it was because you could place a glass of water on the seat while the engine was running and it wouldn’t barely more.
But glasses of water do not ride bikes. I hated the Honda because it had a very low top end and when I took it past 60 mph it would begin to shake.
One day a large truck drove right through me. I escaped with my life only by some very unlikely move. I sold the bike the next week.
Motorcycles were never designed to share the roads with automobiles.
Do you live somewhere where it is summer all year long?
My friend owned a Yamaha 1000 or 1200. I don’t remember which. But it was the most thrilling and most incredible experience I ever had out of doors.
It seemed to me that bike would accelerate 3 times faster than the fastest car I had ever been in.
If I had to ride a bike, I would pick a bike like that because even though I know it is a bad assumption, many bike riders believe it’s better to ride a powerful bike so that they can power themselves out of dangerous situations. I feel the same way - even though I’m pretty sure that is a very wrong assumption. That is just another excellent reason why I should never ride a motorcycle again. There is just something about the lure of riding a bike that makes it intensely attractive and makes my logic and reason just vanish.
But, if there is any truth to the idea that a bike rider can power themselves out of a dangerous situation, I think that could only be valid for very experienced riders. But when I’m being logical, I’m quite certain that is just a very dangerous and mistaken assumption. For some reason, I just think it’s a good idea when I’m either riding a bike or close to riding one. But, don’t believe this.
However, if you ever decide to buy a big powerful bike despite what your logical mind tells you, I strongly suggest you wait until you have at least a year or two of experience riding bikes and that should include riding on many different kinds of roads in many different kinds of traffic patterns.
I wish you the best of luck. But I must tell you that buying and riding a motorcycle is a lot like sleeping with a loaded handgun next to your head in a house full of children. You would just be asking for something terrible to happen to you.
To the original poster. Take the caution of this post to heart, but ignore the opinion. Motorcycles are not for everybody as Charlie Wayne apparently found out. But ridden with attention, skill, and passion they can be one of the most rewarding ways to get around
I have logged well over 200K miles on two wheels and have never been down. My bikes have though! I’ve dropped at least three bikes in parking lots! Stupid stuff like not making sure the kickstand was extended fully.
I’m riding my bike to work today in Atlanta traffic. Looking forward to zipping down the HOV lane past all the single commuters sitting in their cars.