I've found yelp has some decent lists here for venues in Southern California. I'm too new so the forum won't let me post links yet but try looking up "No cover charge bars/clubs Los Angeles and/or Orange County". The lists are pretty solid.
No cover bars/clubs that have kickass ratings are usually good I've found. You avoid the ultra-trendy places that have expensive covers where you can't talk and/or park and if it's highly rated that usually means it's good on at least some nights.