The longer the event the less I "warm up". So if it's a sprint triathlon(under 1.5 hours) then I'll probably do a short stint on the bike to get it in the right gear when I take off and make sure everything feels good. Then about a 10-15 minute easy jog. Finally, throw on my wetsuit and make sure that feels good in the water. The running is the only real "warm up" whereas the biking and swimming is more about making sure I'm ready to race.

For anything longer, I really don't do any warm up. I basically cut out the running. I shake out on the bike to make sure the brakes work and leave my shoe clipped in. I then stretch really easily and just meander around. About fifteen minutes before my start I'll throw on my wetsuit and do a few hundred yards of swimming to get the wetsuit feeling good and adapt to the water tempterature.