Originally Posted by
Koyote
Remove the wheels and turn the axles by hand. If they feel rough, then they are probably open bearing (i.e., cup and cone) bearings that need adjustment - and they might need more grease, too.
Instructions. (You'll need appropriately-sized cone wrenches.)
This is what you need to do first. Having worked on dozens of cheap kid's bikes this past year, I've found almost all of them with wheel bearings that were too tight.