Rather than “don’t buy guys drinks,” perhaps this could be stated as “don’t be desperate.” More to the point, and applicable to all genders and orientations. 
Desperate times call for desperate measures- note to self: moving to a rural Chinese women’s college is a bad idea if you like getting laid! Doh!
Another one:
Don’t move in together just because it seems like the next step. Have some kind of shared vision of where thigs are going, and have an exit plan as well.
If you are waiting for it to get better, stop waiting. Always judge a relationship by what it is, never by what it was or what it could be. This does not apply to a 15 year marriage in which the last 3 months have been hard due to a temporary stressor.
Likewise people, if you are in love with his potential, you are in love with a phantom. Always judge a person by what they do, not what you think they could do, or even what they really wanted to do. No matter how much he wants to stand up to his Mother, if he doesn’t now, he likely never will.
Do not wait for soemone to want what you want. If she doesn’;t want the things that are important to you that’s a dealbreaker, move on.
Never make financial decisions fro emotional reasons. Never become financially dependent upon a partner who has not committed to the relationship in the deepest manner legally available to you.
Edited to steal: “Have an exit plan.”
Do stick your dick in the crazy at least once: it will remind you why you should never ever do it again, and the sex will be unforgettable.
Any two people can have a good relationship during good times (no disagreements, no external problems, etc).
It’s what happens during the bad times that tells whether a relationship is solid. If you can’t disagree without being subjected to insults or threats, or if you’re required to not allow illness, stress, or outside problems to impinge on their life, they aren’t worth you.
If you’re falling in love with someone, pay attention to how they treat other people - service employees, strangers, friends. That’s the person they are, and that’s how they will treat you once the infatuation fades.
The right person at the wrong time is usually the wrong person. Deal breaker level bad timing is not some romantically tragic thing worth fighting for against the odds. It’s just one of a million reasons why a relationship might end up not working. Don’t get caught up in “it could have been so beautiful.” Go find a relationahip that does work.
And on a less flippant note…
Have firm boundaries, treatment you expect, treatment you won’t accept. Make sure the other person knows what these are, and don’t compromise on them, ever.
How they treat you when they are drunk, tired, grumpy or stressed is how they will treat you.
If they don’t respect themselves, they won’t respect you.
You can’t rescue somebody.
No matter how fantastic someone is, they might not be the right person for you. Don’t stick with someone just because they are a cool person. Stick if they are a cool person AND you want to be with them.
If they have never been in a relationship before, that doesn’t have to be a dealbreaker. But there may be a really good reason. Pay attention.
If they have a string of exes and have nothing good to say about any of them, you will eventually be one of them.
Don’t sacrifice your goals and dreams in the throes of passion. Eventually, the passion won’t be enough.
Love is good, but it isn’t enough.
If you don’t get along with their family, be aware that it might come down to a choice, and you might not be the one who wins.
The treatment they accept from others now is the treatment they’ll expect from you later, and sometimes people are complicit in their own unhappiness. When you see them repeating the behaviours that caused the situation they say they want to escape from, no matter how much you love them, you are going to get caught up in that cycle. Thinking that you are the one who can break that pattern is the same as saying “But I can change her!”, and that’s when it’s time to go: it might hurt now, but it will hurt a hell of a lot more later.
On a different note, nobody’s perfect, including you. If your significant other does a handful of things that bug you, he or she probably has a handful of things that YOU do that bug them. In other words, staying realistic about yourself and your relationship will probably make things more satisfying than holding out for perfection (or getting hung up on the little things).
You know, there’s a million fine-looking women in the world, dude. But they don’t all bring you lasagna at work. Most of 'em just cheat on you.
It’s really not all that far from a pedestal to a pillory.
Don’t wait for The One all your life. It’s okay to consider that 0.75 over there and perhaps deciding to round up. Hopefully they will consider doing the same for you.
So is the female version of this “Don’t wrap your va-jay-jay 'round the cray-cray”? 
I know you were talking about your own experience, but this isn’t good universal advice - could prove problematic at a gay bar!
Don’t do this. Really. What it communicates to others is that you are extremely shallow in reality. Anyone who says, ‘Yeah, he treated me like shit, but he was hot!’, has a little learning yet to do.
The first time, sure. More times, after the first time, makes you look like a slow learner!
Looks, being the determining factor, is as offensive, in women, as it is in men, to me.
Mine is also happily married (as far as I know) to “The Bimbo He Left Me For.” And, honestly, I’m happy for them.
(And I think ‘don’t stick your dick in the crazy’ is unisex advice. Sort of like referring to women as “you guys” Or calling people who fight fires “firemen.” It translates.)
Don’t.
Not so much a rule as an observation made by a much wiser Doper than me:
All those red flags you saw going into the relationship? You’re going to get smacked by every single one of them when you flee it.