The lay man approach to time travel seems somewhat strange to me. Let us assume it is possible for a moment. Sorry to lower the tone, but the media (such as films and TV) shows theories of time travel that suggest that time is not linear and it is constantly warping through various states of existance - what I mean is, that if we were able to travel back through time and change events we would constantly be warping through various alternatative existances.
I think it is more sensible to suggest that time is linear. Also, I agree with the theory of time dilation - time may be slowed down or sped up relative to time in a different space - as suggested by Einstein and others.
However, Einstein also suggests that once velocity of matter matches the speed of light it stands still in time. Exceeding it results in reversing time and hence he determined that the speed of light was the maximum velocity attainable (I think) in the universe. I feel this is debateable.
Please submit your own theories or dispute these ideas.