Transition is your time between swim to bike (called T1) and bike to run (called T2.)  You will have a fairly small space, about the width of a normal towel, where you will store you bike and keep everything you need for the race.  Most importantly, this is your space and your time to collect yourself during the race.

Choosing your transition space:  As you enter the transition (secured only for participants) there will be rows of horizontal bars called racks.  Each row will have a sign assigning that row to a certain series of race numbers, for example number 150 to 300.  You are able to pick any space along the length of your row. 

Setting up your space:  Get a towel – and I would suggest an obnoxiously bright, easy to spot colored towel – to lay down to mark your space and lay out your things on.  Your towel should be set up under and slightly to the side of your bike.  Laying out the items you need for your event orderly will help you through transition.  I always leave a little space at the end of my towel, closest to the aisle, that I can stand on to dry the bottom of my feet after the swim.  Next closest to the edge is the things needed first: my socks, bike shoes, sunglasses and helmet.  Furthest back is the things that are needed for the bike to run transition: running shoes, race number, baseball hat, and gel for my pocket.

Other things for transition:  This is your space.  Keep here anything you think you might think you would want or need.  I always have an extra water bottle for the intent of using that water to rince my face, pour on my neck, rinse my feet, whatever.  I also keep chapstick, sunscreen, tissues, spare contacts and glasses.

Packing it all up:  Find a bag big enough for you to easily carry all your things from the parking into transition will walking your bike.