That's like asking which ice cream flavor is best
Each club has it's own dynamic, idiocyncracies and rules... you need to find someplace where you feel you can fit in (or at least conform).
Things I look for:
1) Club must be totally dry... alcohol and shooting don't mix.
2) I prefer clubs that don't allow hunting on the property (or have clearly delineated times/places where hunting is allowed)... you don't want to be shooting on the rifle range and have a hunter pop up over the top of the berm on his way out of the woods. I also a member of a hunting club where no practice shooting is allowed (for the same reason).
3) Obviously, make sure the club has the activities you are most interested in (if you want to shoot sporting clays, make sure that the club has more than a trap field).
4) Water tends to find it's own level... I like to shoot with people who are like me. I don't care about the guy who is bragging about spending the next six weeks in Paris, nor do I care to be around the guy who is green with envy because of what I'm shooting and makes snide comments about it.
5) I won't join a club that has a "junk" range. I have no interest in shooting engine blocks, old TV's etc... it's unsightly, dangerous, and often an environmental hazard.
6) I prefer places that are reasonably clean. I don't mean hospital clean, but at least clean enough where I would sit on a toilet seat if I needed to... I've been in some clubs that don't look like they have been cleaned since the Kennedy administration.
7) Reasonably manicured grounds... again, it doesn't have to be a golf course, but I shouldn't need to wade through waist deep grass... of course, I'm also willing to ride a mower or drive the tractor as needed...
I'm sure if I thought about it I could come up with more... but I'll let others contribute...