Driving through heavy rain.....?

I do a courier route every Saturday, and rainy season has just hit with a florish. The last 2 Saturdays I've encountered heavy rains and this last Saturday I started getting really concerned about some of the flooded out streets. I try to avoid them when I can, but what information should I know incase I underestimate the "puddles" on the road. I want to make sure I protect my car as best I can in these situations.