This is a basic question and i guess thats why i can’t get a clear answer on google. As far as i know you cut a slit in it, wrap it in tin foil and cook it in the oven.
However, do you completely cover the potato or only half cover it, leaving the slit exposed?
What temperature and what amount of time do you put it in the oven?
Are there any preperation other than washing it you need to do before cooking?
Don’t wrap it in foil unless you want a steamed skin.
For a baked potato with a crispier skin, wash the potato, pierce with a fork several times and bake au naturale.
When done, cut the potato in half, gut it, put lavish quantities of butter, salt and pepper inside the skins and eat them as a separate item from the spud.
Or not.
What temperature do you set the oven on and for how long do you cook it?
By the way, you also need to remove any sprouts and eyes when washing the spud and trim off any bad parts. Also, coat lightly with vegetable oil for added crispness. Time will vary with the size of the potato, but generally can take up to an hour at 425.
If you don’t care about the skin, then nuke it for about 5 minutes.
Scrub well. A few slits. No foil wrap. In the oven at 350F for ~40 minutes (never in a microwave). Great for stuffed potatos and skins, after they cool, as well. Was on FoodTV, can’t remeber the cite 
You can bake a potato at any convenient temperature from 325 to 450 degrees. Obviously how long it takes depends on what temperature you select and how big the spud is. A medium potato at 350 will take about an hour.
Scrub it well before you put it in the oven. Some folks rub the skin with a fat of some sort – veg shortening, bacon grease – others just leave it alone.
Strictly speaking a potato cooked while wrapped in foil is not a baked potato at all, but a steamed one.
You can cut cooking time by up to half by running a skewer (or even a long clean iron nail) through the long axis of the potato. This will carry the oven heat to the center of the potato [potato flesh is remarkably good insulation. a potato sized chunk of meat could be inedible after an hour at 425. Make sure that at least 2" protrudes to absorb heat from the oven.
This works if they’re wrapped or not, though of course the skin of a naked potato baked this quickly won’t be quite as crisp. I usually rub them with oil and raise the temp to 450F or so to compensate. I also turn the potato at about 20 min for more even crispiness) To test for doneness, probe with a fork. It’s done when it offers little or mild resistance. (according to your tastes) The potato will keep cooking somewhat after it’s removed from the oven, especially if foil-wrapped.
You can keep them warm by placing them in a loosely sealed tupperware container lined with towels. A crispy-skinned potato stored for a modest time in this way will recover most of its crispness after air-drying in the oven or under its own heat.
I mention this because it’s not always practical to put the potatos in an hour ahead, especially if you want to use the oven at a lower temp for other parts of the meal. Your oven, and experiences, may vary.
-lv
And unless you are Celyn, you will be cleverenough NOT to use the fork or skewer as a convenient way to pick up the finished article.
OUCH!
I usually only eat the really big potatoes (two pounds or so).
I wash well, wrap in paper towels, and slap in the microwave for 10 minutes. Then I poke with the skewer and bake at 400 or so until squishy (10-15 minutes).
OR… you can grill them. 
Wash the potato.
Poke some holes in it with a fork.
Slap it in a Microwave oven for 4 minutes.
Let it sit a couple minutes.
Slice or break it open.
Apply condiments to the inside of the potato as desired.
Eat it.
Foil is common at certain restaurants, and is very popular with picnickers.
The foil tends to distribute the heat, so that for example if you bury the potatoes in the ashes of a hot campfire, they will bake more evenly.
Also, they will not cool too quickly between removal from the heat and presentation to the customer.
If you place the potato in a metal pan, or even straight on the oven shelf bars, putting the end of the skewer in direct contact with the pan or bars will pump more heat into it, cooking the potato faster.
I keep a handful of new ten-penny nails in the silverware drawer just for baking potatoes. The first time my wife (to-be at that time) saw them, she reached into the drawer, held one up, and said “Baked potatoes, right?” From that moment on, I knew she was a keeper! 
Foil: never
Microwave: NEVER
Poking holes in it: unnecessary
Skewers: Speeds up the process, but that means less crispy skin.
My recommendation is rub olive oil, garlic and salt into the skin, then put into any medium-to-hot oven. And if it’s ready in under 90 minutes, the potato wasn’t big enough
Alton Brown of the Food Network has a good easy baked potato method. Ever since I learned this, I cook my baked potatoes this way:
The oven temperature can be anywhere from about 250 to 450 degrees F. The potato will cook quicker at higher temperatures, that’s all. I don’t really bother with trying to bake potatoes at any particular temperature, I just throw them in the oven with whatever meat I’m roasting and don’t particularly worry about it. Generally, when the meat’s done, the potatoes are done, or close enough. If I’m baking a quick cooking dish, I throw the potatoes in the oven earlier than the main dish. Cooking times will vary according to oven temperature, size of the potatoes, whether or not you use a metal conduit, and the phase of the moon. I use medium small potatoes, as we really don’t need the huge monsters that are sometimes sold as bakers. One of those monsters is more than enough to serve all three of us. Poking a metal skewer (nail, whatever) WILL help cook the potato from the inside out, make it a bit mealier (which is a good thing in a baked potato) and cook it quicker.
To sum up: scrub potato well, removing any eyes, sprouts or bad spots. Poke skin with fork. Rub with fat/oil if desired. Thread onto metallic object if desired. Throw into hot oven. About an hour later, poke with fork to test for doneness.
Many purists, by the way, only put butter, salt, and pepper on their baked potatoes, eschewing sour cream and cheese and bacon bits and all the other goodies those of us who are less pure load the spuds with.
Some varieties of potatoes make better baked potatoes than others, but you can bake ANY variety and have it turn out pretty good. It’s really very simple, it just has some variables.
Leftover baked potatoes can be reheated as is, or mashed (with or without skins) with milk and heated for mashed potatoes, or diced and made into potato soup, or diced and made into potato salad, or…well, you get the idea.
If you’re starting to cook for yourself, I advise that you pick up a copy of Joy of Cooking, in paperback. It has a lot of really basic recipes and techniques, and will give you guidelines such as “Roast a chicken at (whatever temperature) for (x minutes) per pound.” Such guidelines are very helpful when learning to cook. This book also has lots of fancier recipes.
For the beginning cook, I also suggest buying a vegetable steamer and using it to cook fresh or frozen veggies. Steaming veggies really brings out their flavor, and even if you think you don’t like a particular veggie, you should try it steamed, with minimal seasoning at first.
By buying those two items, (the book and the steamer) you will be able to eat better and more cheaply.
I strongly advise AGAINST turning the oven on in the summer in moderately hot climates, as it will quickly heat up the entire house and cost quite a lot in air conditioning fees. I live in Texas, and I just won’t turn on the oven for about 8 months out of the year.
Scrub well, rub with olive oil, coat with kosher salt, bake directly on the rack at 350* for 1-2 hours depending on the size of the spud. Cut it open, add a pat of butter and a bit of salt and paper… I could eat a baked potato every day of my life.
Would roughly the same cooking times and temps work for sweet potatos?
Yes, Brutus, although since sweet potatoes are generally larger than “regular” potatoes, they may have to cook longer before they’re done (test by seeing if they feel slightly ‘squishy’).