The key to success on AFF is to realize that meeting people is no different than in person. You need to treat people with class, humility, and humanity and keep it low pressure. Just because you are on the internet doesn’t give you the right to constantly harp on sex, use lewd and obnoxious sexual references in all your emails, or pressure women about sex. Treat it as if you were meeting a new friend. You should be open minded and interested in learning about your new acquaintances as people. If you try to get between a man and his wife, tell her you are better than her husband, or appear that you might fall in love with her if you fuck her, you will be 
deleted without a second thought and possibly blackballed among that couples friends as well.
Remember, you both are there for sex so you needn’t worry about that, it will happen if a mental connection is there (And for many people the sex will be more frequent and kinky than they have previously experienced). That’s the beauty of AFF, unlike meeting at a bar you can forget about whether or not you are going to get lucky. You can be assured that if you can forge a mental connection you will get laid, it’s one less thing to worry about.
Above all, be honest about yourself and your dating situation (cheating men are sometimes tolerated, but lying cheats are NEVER given the time of day), be open and friendly, and don’t expect that women on AFF are any different from women in real life
They are still people with feelings, desires and aspirations.