I can't find a darn video - my Google foo failed - but I remember dudes in Star Trek being beamed up in all sorts of positions (lying, sitting, being carried) and I imagine teleport the same way.
If you teleport off a ladder onto the ground, make a balance check or topple.
On Star Trek, any time on a person is teleported to a location that is not directly below the Enterprise, they are rotated in some way. The curvature of the planet requires it (see my post above). Otherwise, they would land lying down, upside down, or on an angle. Likewise, any teleportation from one ship to another requires rotation (unless there is some magical force holding the ship to be perfectly planar to each other).
OTOH, in Star Trek, the position of the person's arms, legs, etc, in relation to the rest of their body remains constant. I don't know the name of the episode, but I specifically remember an episode of TNG where they teleport a mountain climber aboard (thinking he is in trouble), and he comes through in the exact position he was climbing it.
So, if you want to imaging D+D teleportation to match ST teleportation, it could rotate the character from prone to upright, then require a balance check to stay standing from the instant gravity change.
Hassassin said:
If you teleport into a room with Reversed Gravity, do you appear on the floor or the ceiling?
You appear at the exact place and rotation you intended to. What direction you fall in is a completely different question.