I think cheating is really wrong... HOWEVER, if you did want to cheat on her and did nto want her to find out, the whole deal is really a fucking science... first off, when you meet a bitch you want to fuck, try to fuck THAT DAY, tell her you just broke up with your girl, fuck her that day then a couple of days later tell her you and your girl got back together, she might not have any feeling for you that soon so she'll be more likely to wish you good luck and walk away...
OR if you can't fuck that day, don't hide the fact you got a girl, put it on the line and tell her you have a live-in girlfriend, she'll either accept it or walk away... Most chicks will walk away, but the few that will stay won't fuck your shit up. SHIT! if you are ever hanging out with your side ho and your GF calls just tell the side Ho "shut up, my girl is calling me"! thats when you know the bitch is a trooper!