You have decided to do your first triathlon. How do you decide which race to do? Firstly have a look at the website of your state triathlon association. They should list all the potential races in your area.
It is better to start with a race distance that you think you will easily be able to handle. If you are struggling to cover the race distance in training (especially in the swim), attempting to race that distance might either kill you or kill your desire to ever race again. Better to start shorter, and step up in distance later.
Choosing a course close to home is not a bad idea, as long as the course caters for your ability. If you are a weaker swimmer, staying out of the ocean for your first few races is a good idea. The ocean (even bays) can get very rough. Weaker swimmers will also benefit from a wetsuit swim, so choosing a race in the early season when wetsuits are most likely to be allowed is not a bad plan.
If you lack confidence on the bike then a less crowded race will allow you more riding space. Also look at the technical aspects of the bike. Too many corners, roundabouts and speed bumps are not great for the first timer.
Another important consideration is playing with friends. Your race day will be much smoother if you go with a more experienced athlete and they can give you a few pointers. More importantly you have someone to have breakfast with after the race!