how to pick my first tri-bike

Hello everyone

I'm new to the sport of triathlon. In fact, I haven't participated in a sport in a _very_ long time. But, I'm excited and committed to putting at least one triathlon under my belt.

And since I'm new to the sport, there's alot I don't know and I have alot of questions.
Here's one question: How do I pick my first tri-bike?

I've seen several threads from folks asking which bike to choose, once they've narrowed down the field. But, my question is a little more general. I understand picking a price range before shopping (this is always a good idea when spending more than $100, IMHO). And there is also the recommendation of knowing what accessiories/components I will want ahead of time, too. However, I'm not sure where to look to educate myself about the different components, to learn what accessories are available, or even how to pick a frame size.

Can any of you recommend a resource?