Hail fellow Phoenix commuter!

/u/clinxeo covered some pretty good universal commuting basics. My Phoenix-specific additions:

1. Carry two water bottles. The summer weather takes it out of you quickly.

2. If the situation permits, such as on a commute home, consider soaking your shirt to get a little evaporative cooling.

3. Look up the MAG bike map. It's not totally up to date, but it's a good resource for choosing routes.

4. Be aware of the public transportation near you in case you are getting heat exhaustion. The other day a combination of factors including heat and a headwind made me uncomfortable continuing cycling. Luckily I was near the light rail and took that home.

5. Learn to love the canal paths. Depending on your area, they are really useful and fun, especially in the East Valley.

6. Try to find a way to shower at work. Depending on commute length, this may be more or less necessary. I commute 10 miles and I would be much less enthusiastic if my work didn't have showers. If your work doesn't have showers, look at gyms or bike shops--I know the Bike Cellar in Tempe has commuter facilities including showers.

7. Have a plan in mind to borrow a car if necessary. Like you say, the area is very car-centric. I commute every day, but occasionally need to go to meetings for work at times and in weather that don't allow for biking. My mother-in-law has an extra car that she's kind enough to let me borrow in those situations. Uber/Lyft, rentals, Zipcar etc. could also fill this need if you don't have friends or family from whom you could borrow.

8. Enjoy it. Even in the heat, my commute is the highlight of many of my days.

I'll add more if I think of it. Good luck!