Literally wrote a tutorial about this today here. It will leave you with an optimal route in Google Maps, based on whatever orders you have in your store:
We just launched EasyRoutes, the easy way to create local delivery routes, as a free app in the Shopify app store.
You can select the orders you wish to deliver, click the "Generate Route" button, and the EasyRoutes app calculates the most effective, economical route to help your drivers drop-off their deliveries as quickly as possible.
EasyRoutes uses Google Maps to optimize local delivery routes for your Shopify orders, allowing you to take advantage of Google's traffic and time-of-day data which helps you drop off your deliveries faster and more efficiently.
Hope this helps!