I was going to post this tip in a seperate thread, but this'll do:
Requests can make you look and feel like an idiot - people always ask for what you don't know, and sometimes by the dozens. It's not possible to know everything and even if you learn the "most requested songs" it's almost a certainty that you won't get asked for those songs again (I learned "Lara's Theme" from Dr. Zhivago after months of repeated request, and sure enough noone asked for it again after I learned it!). So I started printing and giving out a list of 200 songs that I do know. 200 songs doesn't sound like a lot but when you print them out by song title it's actually very impressive. And I've come to find out that people just ask for songs to be involved in the act; not because they especially want to hear something in particular (except for the couple that asks for their wedding song or such). 
So rather than wait for requests I now visit tables and give patrons my "song menu" and invite them to choose from the list. I do this at the beginning of a break and revisit the table just prior to going back on stage. Their first reaction is always "you know ALL of these songs?" or "that's quite a list!", and then it's suprising to see what they actually choose - it's often something I wouldn't expect. But at least I no longer suffer from the embarrassment of called-out requests that can make me look stupid... and my tips have improved!
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Jim Eshleman