Want to do a dry run...

X2 on what the previous person said.  The bike to run is what I would focus on.  Knowing how you body will respond after the bike is so helpful.  It will give you some sense on how long it will take to get your running form and pace going.  I am no expert but being a newbie I do at least one to two before each race (did one this morning at the race site for my next sprint).  I was able to get a feel for running up the first hill right out of T2. 

The other thing that I have found helpful is to practice your T1 and T2 transition a couple days before the race to develop your Transition routine.  I generally set-up a transition in my garage entry using a 1.5" PVC pipe hanging it to replicate the bike transition stand and run tot he bike with my wetsuit on, removing my wetsuit (much easier when it is wet) as if I just got out of the swim, con't. on and take the bike up the street  a block or two and return and go through bike to run (T2).  This has been very helpful for me to make sure I work out any kinks before hand and re-set my routines.