Just general driving etiquette is what's really needed. Give your opponent room, and hope he returns the favor, don't block more than once, respect others lines, and don't drive too aggressively. I mean really, that's all there is to it. If you're burning up the track right behind me, you bet I'm going to yield to you. Why? Because there's absolutely no logic in blocking you and potentially screwing us both out of a decent finish. That happens more often than anything, someone is constantly blocking the man (or woman) behind him, and the other person isn't going to give up that easily, and why should they? I mean really, you're the one who refuses to back down when you should be, so the person trying to pass by becomes more aggressive, and at some point it's almost certain one or both of you will be in a sand trap because of it. If it's the last straight on the last lap, OK, it's more forgiveable. You haven't been blocking the entire race, and now it's victory lane, no, you shouldn't have to give up your win in that instance, but if you're bobbing and weaving the entire time just to stop someone from a legit pass, I feel no sympathy when they've finally had enough of your *you know what* and just take you down. I don't agree with dirty racing, but I know when someone is right and wrong.
Also, if you're an aggressive driver, don't go crying when someone decides to start pressing you. If you have a bad habit of, as poster above referred to it, barge-passing, don't expect me to go out of my way to accomodate you. I'm going to stick my line, and I don't care if it results in you being off the track. You want to pass on the inside, fine, do it after the apex and make sure you're fast about it, because I use the entire track, and if you're at my side when I'm trying to set up for the next time, so be it, gravel pit for you. Now if you can fast out and be in front of me, please do, but if you can't pull that off, pick another moment to pass, because as I said, I'm not going to inconvenience myself because of your aggressive actions. I like to race good and clean, but if you're not willing to meet me halfway, I'll continue racing my best but I'll be that much less likely to do things like yield to you, or give you the pass in a corner.
It's all case by case for me. If you're driving far too slow, I'll pass you in a turn, but I won't be reckless about it. Get up there and in front, don't screw around with it, and if you're unsure, it's best not to do it. I think of it like reality, and ask myself "Now if I were a pro racer, and this happened on a track, would I normally do this? Would this be extremely hazardous to myself, or the other driver? If he did it to me, would I be upset with his driving methods?" and depending on my answer, I go from there.