It's kind of tough to give you advice without knowing what your goals are.  The advice for a sprint is very different than the advice for iron distance.  Also, how competitive are you looking to be?  Racing for completion?  Racing against your own personal times?  Trying to qualify for Kona?

Regardless, here are a couple of generic tips.

1. Practice transitions before race day.  For your first couple races you should focus on making sure you don't forget anything.  Would suck to go out on the run and forget your race number.  Organize race gear in piles before the race to make sure you will have the correct items for each transition.

2. Based upon your post I would recommend you focus on swimming for a while.  Just estimating your ability based upon "cycling about 200-300 km/week" and "swimming lessons coming up" it seems like you are a much strong cyclist than a swimmer.

3. have fun!