I don't seem to have this problem.. I find it easier than any other place to get dates, and personally I find it better if you do it earlier in the day. It's hilarious when they make comments about how you are drunk but then realize you've been drinking water when you order another one. For the one's that are on autopilot, just call them over and ask if they are single.. They usually know which of their coworkers are single or not, so you can actually ask around if you do it without looking sleazy.. "Damn.. well you're all so cute which one of you isn't single?" (I don't use this, it's conjecture..).
I've also started a game once by asking if they are required to say they have a boyfriend, and then if they say no (or maybe yes..) you can tell them to bring others over to test this "theory" you have. It also makes you feel like a pimp having hot women brought over to you while you relax.
Other things that my friends have done to lighten the mood and keep them on their guards is to ask them what everyone's name is, or if they remember. You can introduce themselves after they introduce themselves as their waiter, and then quiz them every so often. Mix around the names just to keep them on their toes and to tease them. I also like to pause and make the waitress nervous a little bit when speaking.