You’ve set up your transition as suggested in Triathlon Set-Up Routine. If not, you should.
You are now in the water waiting for the start. Naturally, you have put yourself in the correct wave and the correct place for your ability.
Even more naturally, you know where you are going.
You have a bit of water in your goggles to clear your lenses with when they fog (shake your head, splash the water around inside the goggle and voila! Clear vision again).
You are ready to go.
Last minute announcements and BOOOM! Start is given.
I suggest you take the first 20-30sec and gently get faster, find a good set of toes to follow and hang on for dear life.
If those toes are not going in the right direction, like seriously off course, let them go. If they are zigging and zagging just a bit but generally going the right way, stay with them.
Swim is done.
Swim to bike transition begins
Swim as close to shore as you can.
Remove goggles and swim cap.
Begin running to bike
Unzip wetsuit and remove top portion.
Continue running to bike
Arrive at bike
Remove rest of wetsuit.
Sunglasses on, helmet on (yes in that order—keeps the helmet straps on the outside of the sunglasses so when you take off the helmet, sunglasses can stay on)
Race belt on
Grab bike and go.
Bike to run transition begins
Dismount bike at dismount line
Run/walk carefully to transition spot
Helmet off (surprise! Your sunglasses stay on)
Optional hat on
Optional socks on
Grab optional nutrition (which you should not need much of—that is why there are aid stations)
Away you go.
Just like the swim, take the first 20-30sec and wind your way up to speed. This will save you from going into oxygen debt, which really is something to avoid.
I hope this helps.