Harley alluded to "only wanting you around when family and friends aren't." Yep. If he doesn't want you to meet family and friends, I think it's a safe bet you're not the only pond he's fishing in. There is a reason he doesn't want them to know you exist, and that's so nobody accidentally lets it slip. Like maybe to his wife.

The waitress test comes up a lot, for good reason.

I'd watch what he says about other men in relationships. If they treat their wives/girlfriends with respect, take their feelings into consideration, or even just remain faithful, and he calls them "whipped" or cruder terms, it's obvious he's not going to treat you well. Even if another man's wife or girlfriend does do something questionable, and your date says, "If my wife/girlfriend did that, I'd lay her out on the floor," I'd take it as not an exaggeration, and that would be our last date. Nowadays, anyway, now that I know better. I didn't used to pick up on that kind of cue, and I'd always pay for it later.

Another site adds, if something major happens (his mother died, his sister had a baby) and you're not on the list of people to call and give the news, you're not an important part of his life. My own thoughts on that are, well if that happens and you confront him on it, expect a guilt trip. "My mother just died, and you're picking this time to dump me?" Well, yeah. If I'm not enough of a factor in your life that you would call and tell me, then you shouldn't miss me very much. I'm sorry for the loss of your mother, but I'm no longer under the delusion that we have anything together.