On touchscreen devices, you can tap and hold on the screen then use the menu to save the location. From the Drive To menu you can the go to Saved Locations and add that location as a Favorite.

Now if there were only a way to sort the favorites list so that the top three that show up on the "Drive to" screen don't happen to be the first three favorites I happen to enter. Maybe they could be weighted by usage if you are not able to allow us to sort them manually. It would save an extra screen load if the top three were our most used locations. I often know the route, but use Waze to anticipate if I need to rush if I'm running late. It's a good estimater of my arrival time.

Reorder of favorites is coming. The edit panel is in the latest beta for iPhone, just not fully functional yet.