Once your transition is set up walk through transition 4 times, from swim entry to bike exit and bike entry to run exit. Slowly visualize yourself racing through transition.
Sit in transition for 5 mins after you have set up your bike. Watch the people around your transition space set up their transition, make a mental note of their equipment, this will help orientate you during the race.
In shorter distance races such as Sprint or Olympic Distance, break two elastic bands and tie them around the top tube of your bike, then place your energy gels underneath the elastic bands so they are easily reachable during the bike segment.
Same idea with your Sunglasses which during the rush of transition can easily get forgotten, dropped or trodden on! Place the arms of the sunglasses underneath the bands to hold them securely, then you can wait until you have got yourself into a comfortable position on the bike segment before putting them on.
In a Duathlon use two pairs of running shoes one pair for the 1st run and one pair for the 2nd run. This will save time as you will not have to think about where you place your running shoes in T1, as well as then being able to put on sweat free, pre-positioned shoes in T2.
The swim is the 1st part of the triathlon so make sure you do 5 to 10 mins of shoulder mobility exercises before getting into the water, whilst doing these exercises it gives you a good opportunity to visualze your whole swim from the start, right through to running into transition and finding your bike.
Try to get into the water 10 mins before the start of the race, this will help you get acclimatized to the water temperature, as well as help your orientation of the swim bouys.
Stop your goggles steaming up by putting a small amount of washing up liquid or shower gel on your finger tip and rubbing the inside of your goggles, allowing it to dry before the swim start.
Always take a big mouthful of water from your race bottle after eating a gel, this helps increase the speed of gastric absorption by diluting the carbohydrate percentage you have just eaten.
If the water is cold wear two good swim hats. Pull them well down over your ears thus preventing the cold water from entering your ears. This really does stop that horrible dizzy feeling. If you really suffer with this problem consider wearing earplugs.