Use one that was given away on some random sales rep, would go without, but my MS Laser mouse refuses to track on me desk, as its rather glossy.
Don't use one myself, then again, I'm using an exotic dell mouse. Tracks well on a standard beech veneer desk, took a while to get used to my home made desk at home, it struggled with the glossy black worktop. Personally I can't stand mousepads, I like my setup minimalist and a mouse pad just irks.
steelpad 4D or creative x-fi cloth one from i30, depending on what mood im in... i find no mousemat makes sweaty desk.....
I had a mouse pad my mom had made with my sons picture on it, it started to wear out and I wanted to keep it nice so I just busted out the free max pain pad I got years ago.
Well, I use an everglide mousemat, and to be fair it's pretty good, but I wouldn't have got it if I hadn't won it tbh, I'm usually a cheap and cheerful guy c.u.later
I roll with an Icemat. Kind of hard to keep smooth since it's glass, but it's really slick for a few days after I clean it.
Black Icemat + thick teflon skates on my mouse, and I use my old steelpad 4D as a rest for my elbow/forearm. Mouse mouse!
Generally I use whatever surface is nearest - desk, bed, leg, etc... If I'm gaming I'll use a basic mouse mat.