What happens when you attempt to teleport to a moving object like, say, a ship on the ocean or onto the back of a moving horse?
The only ruling I can find in the spell description is: "You must have some clear idea of the location and layout of the destination".
I imagine it's not a big deal if you can see the destination (through scry or whatnot).
Also, should the spell caster have to remain in the same position when they arrive? (Could a wizard teleport to his lab desk in a sitting position instead of the standing position that he was in when he cast the spell?)