i recently cleaned out my bearings for the first time ever and they run even smoother and faster than when i first bought then 2 years ago.... total cost of the cleaning materials was less than 20 bucks so im really stoked...
1) remove bearings from wheels and pop the shields off. I assume you know how to do this already so i wont explain any further.
2) soak the bearings in methylated spirits using a glass or metal container. if you have a cap for it, pop it on and give the bearings a good shake to remove all the dirt. after that let them soak for a bit (30 min).
3) now you need to dry the bearings. i soaked my bearings in alcohol bought at the hardware store for 5-10 minutes to remove any moisture on them.
4) remove the bearings from the alcohol and wipe them dry
5) lube up the bearing with some kind of lubricant except WD-40, which will fuck up your bearings bad... you can use the powell speed cream or some 3-in-1 silicone based lube
6) fit the bearings back on your board and skate.
alternatively, you can try finland's windex method, just use the search function to find it... he swears by it but i would never try putting windex in my microwave...