Focus of my question is given in the title.
More generally, which movement options a prone creature has?
I am aware of the 5-ft. crawl and the stand up (both move actions that provoke an attack of opportunity).
Example given to further clarify.
A gargolye standing on the ground has been tripped (thus falling prone). On his subsequent turn may he use its fly speed to move away and gain altitude directly from the prone condition?
Must he stand prone before taking flight?