We spent an afternoon teaching Alijah how to ride a bike using a method we learned by watching a Bike New York video on the easiest way to do it (they're a non-profit bicycle organization in NYC.) Basically, you remove the pedals and let them get comfortable just scooting around with their feet and getting their balance by pulling their feet up. Once they have that down, you put the pedals back on with the knowledge that they already know how to balance.

It worked great, as you can see in the video. He went from not knowing how to do it, to pedaling on his own, probably within an 60-90 minutes!