Timing and Sending Data

Obviously timing is critical to a client displaying the correct state. I have though up some simple and not so simple and high bandwidth methods of ensuring this works. What method do you guys use? In general is it better to use tcp so you don''t have to implement your own form of ensuring that critical packets are recieved? Should I use TCP for game state messages and UPD for non critical updates like messaging, scores, blah? I was thinking that ever tenth packet might be where the client sends off its current location and the nine packets in between would be containing things like ''player 4, FORWARD, JUMP''. The tenth packet would be to ensure that if something screwed up in the command delta''s to be played in the world then it would be corrected not to far in to the future. I''d also make this packet based rather than time based so that a player not moving(camping, chatting, healing,taking aim) would not be using and bandwidth. Is that a reasonable assumption Is there anything I''m missing in the things I''ve been talking about over few days? Thanks gimp