There are different methods of bow, therefore different ways of teaching it. I probably can't help you, but jic, we would need to know the end result you want (maybe find a picture on the 'net as a sample) and what initiated the bow today.
As an aside, please don't double post. Then we loose track of who is saying what.
Well it would be hard to find a pix (partially because I don't know how to do that...it wouldn't let me ^^') and he was doin different bows one leg/knee on ground with head neatly tuckd in and other leg out then it was only half bows after that really....
You can pass the leadrope between his front legs & pull his nose down & in using one hand while you hold up one of his front feet with the other hand. Once he's down, give him a treat & let him right back up. If he's smart he'll catch on quick.
Stacy Westfall and Ken McNabb both have videos showing step by step how to teach the horse to bow. Stacy used the bow with her horse so that she could mount her bareback/bridleless reining horse from the ground! Stacy and Ken use different techniques but got similar results; Stacy had emphasis on having the horse stay in the bow until she gave the cue to get up, so that might help you.