I feel this node should be expanded on.
Fire Spinning has evolved into more than just poi. There are fans, staff, sword, helio and dragon staffs, snakes, hoops, eating, breathing, and that is just a few.
It first should be said that fire spinning is dangerous and stupid. You should not do it. That being said, I do it and love it. Coincidentally, I also teach safety classes on it. That will be another node some day.
If you are going to do it, do not do it alone, and do it sober.
Fuel - The other write ups are correct - do NOT use gasoline. White gas, also known as camp fuel, is ideal. It evaporates quickly, burns relatively cleanly, and is not quite as volatile as gasoline. Relatively speaking. In some countries you can not get it, so kerosene is used. This is not the worst fuel, but it's oily, smoky, and very dirty. Sometimes lamp oil (paraffin) is mixed with the white gas to help props with smaller wicks burn longer.
Props - There is a huge variety of props out there - you name it, you can find it. Within the prop category is yet more variety. Size, design, and amount of wick varies dramatically. It seems that performers who prefer more tech heavy trick like smaller, lighter, easier to manipulate props, and folks like myself who may not excel at fancy tricks go for bigger, flashier props.
Movement - This is probably one of the hardest parts about spinning, if you are not a dancer to begin with. People who have studied martial arts also seem to translate the movement effectively to fire spinning. For those of us not blessed with grace, you have to practice. Not just the moving part, but also attempting to let go of being self conscious. One of the best classes I ever took was called "Dancing with your props" and spoke a lot about not relying on your feet and props alone, but allowing other body parts to "lead" and letting your flaming prop and feet follow. It made a huge difference in my comfort level with not just moving, but with my body in general.
Clothing - also mentioned in the other write-up, stick with natural fibers. Cotton, leather, wool, silk, and your own skin truly are the best options. Primarily because they do not melt and take some time to actually catch on fire, giving your safety time to put you out in the event of a significant fuel/flame transfer. Anything plastic based (polyester, nylon, etc) will melt into your flesh if there is a significant fire accident. That will result in a trip to the E.R. and a fair amount of horrific scrubbing as the clinicians remove the melted debris from your body.
Practice - This is actually the most important piece - short of NEVER SPIN ALONE. Practice with your props a LOT, long before you actually burn them. Get familiar with them, their parts, the space you need to safely maneuver them, and so on. This will go a long ways to ensuring your first burn is not just successful, but satisfying.
If you really want to learn to do this, find a local flow group or teacher. It really is something best learned with a hands on approach and with experienced people. This way not only with you (hopefully) learn to do it safely, but you will be with folks who stay calm if something does go wrong, who can handle it quickly before anyone gets hurt. You will, eventually, get burned sometimes. It happens, but do everything you can to prevent it.