Here's what I had for my transition area (laid out in the order in which I would use it)...
--Towel to lay stuff out on
--BIKE HELMET--put it on first so you don't forget it
--towel (to dry feet if necessary, but I don't think I used it)
--socks, which I had laid out in the shoes
--bike shoes (I have clipless pedals. If you don't, I would just wear your running shoes)
--gel, which I put in my tri shirt pocket (if it had been a longer race, I would have taped them to the top tube on the bike)
--sunglasses
I think that was actually it for the swim to bike transition. I had the water bottle in its cage on the bike. I already had sunscreen on. I didn't need to put on or take off any clothing. Pretty much just get helmet and shoes on and go. They didn't require us to wear the race number during the bike, so didn't need to do that then.
For the bike to run...
--race number on an elastic/race belt (so you just pull it on and don't have to worry about pinning anything on you at that point)
--running shoes
For a sprint, I didn't wear my fuel belt (for water/gels). Your water/fuel needs may vary, so think about what you would want to have with you.
I'm probably forgetting things, and I only did the one sprint, so others will have more to say.
Maura