Well I'm in week one and it's going pretty good. But I feel like I've done more right than wrong.
Here are some things that have really helped:
1) Good Gear
When I decide to do something, I tend to go full on and get the best tools I can afford for the endeavor. I didn't go super high-end on everything, but I got some good rain pants, Gore-tex socks, good base-layers....all the things that would help make my ride comfortable. I knew if I was miserable, my excitement about the bike would quickly fade.
2) The Route
I did a lot of looking at Google Maps and street views, as well as driving different routes to and from work before starting the commute. I chose a route that minimized hills. This included a long waterfront stretch of sidewalk off the road. Part of the urge to start biking was the desire to get into better shape and drop weight. But I needed to acknowledge that I had to work into it, especially the hills.
3) Minimizing Traffic
Either by the route or the timing, it was important to me to get some rides in where I was just getting comfortable with the bike and the roads, not worrying too much about drivers.
4) Doing Whatever is Safest
I've really been observing other cyclists since I decided to start commuting. Some are very aggressive about taking the lane, others seem to stick to the sidewalk and use crosswalks as much as possible. In the end - it seems to me that it's all about whatever is safest. If there's an intersection I don't feel comfortable with - I will ride up on the sidewalk and use the crosswalk. I just don't think I should limit myself to one way or the other.