I try to ask between $100-$200 (US) per person, per day. A smaller guarantee versus a percentage of the door, whichever is greater is also usually acceptable. Our friend Art Thieme chided us once years ago for charging too little. He said, you can take the $50.00 gigs if you want to. But for some other venues you can always ask for an amount and come down, if it's a place you really want to play. It's really hard to come up in price. I found Claire's advice, above, very fitting.