I see a lot of people who either NEVER clean their bearings, or do it improperly when they DO clean them. I've seen many different ways to clean them, so I thought I would make a standard for cleaning. Here it is, enjoy!
Step 1: Remove the Bearings
The video explains it all (albeit in a rather stuttery and halting fashion).
Step 2: Taking Your Bearings Apart
I used a dental tool to remove the rubber seals from the bearing. If you have a steel bearing cap (see image #3), then look for a little c-clip in the side of the bearing case. If there is no c-clip, then just skip this step.
Step 3: Cleaning the Bearings
Put the bearings in a container WITH A LID and fill it to the brim with isopropyl alcohol. Cap the container and shake for 5 minutes. If your bearings are still coated in nasty, repeat the process.
Set the bearings out to dry.
While you're waiting for the alcohol to fully evaporate, you can take the time to clean the bearing covers with some paper towels.
Step 4: Re-Lubricating Your Bearings
If you were able to remove your bearing covers, then get hold of some gel lubricant (picture #1). If you couldn't, then procure some 9-weight gun oil (picture #7).
The rest of the instructions for this step are in the pictures.
Step 5: Putting Your Wheels Back Together
The best way to work the lubricant in is to RIDE THE BOARD.