Hmm...I really like SadieKate's post. Since you fell, maybe try this...

Clip in with one foot while astride the bike.
Do not sit on the saddle.
Raise clipped-in foot to about the 2 o'clock position.
Push down hard with that foot to get you coasting at steady pace.
Clipped in foot should now be at 6 o'clock position.
Still, do not sit in saddle.
While coasting, have all weight on foot that is clipped in.
Clip in other foot.
Sit on saddle.