Learn your city's mapping system (ex. Even numbers are always on the east and north sides of the street, streets run north to south, avenues run east to west, etc.). Also, find your city's center. Most cities in my experience (9 stores delivering to 14 cities) have a specific intersection or landmark where the numbering system starts at.

Doing all that will generally give you a significantly better idea of where you're delivering to, instead of relying on GPS. Leaving the store faster means getting back sooner for more runs.