I'm talking about the wheel bearings. On the rear, the bearing is sealed so you will want to clean it really good with solvent (alcohol) then get some speed cream from your local skate shop (or another suitable light bearing oil) and lube it up. On the front, remove the axle and loose bearings, clean the bearings and race, then repack them with a suitable grease. I use white lithium grease. Don't tighten the axle too much, just enough that there is no play or wobble.