Wow. All this, "take a test run on the weekend" talk is rather surprising. That would be nice, but I've usually got stuff to do on the weekends, (I don't know what that stuff is until my wife tells me, Friday evening).
Being a career freelancer, my assignments take me to different parts of town on a fairly regular basis.
I check the route at www.gmap-pedometer.com and just go. I also check to see how far it is from train stations, (some days it's nice not to fight the headwinds). If I have a long-term gig, I will alter my route from time to time.

This may not be the best way to go about it for everyone. It works for me, since during my first two years of college, I was a delivery driver here in the Dallas area. It taught me a lot about how the city is laid out.