The iPhone works pretty well as a navigation tool. You could utilize the in-built map facility for finding your way around unknown areas that you are visiting. You can bookmark the map feature for easy access on your phone.
The iPhone battery runs down quickly. Particularly, if you use your phone a lot, you may find yourself feeling helpless if the device dies right when you need it. Get in the habit of keeping it plugged into an electrical outlet whenever you can; this will help make sure the battery is charged up during the day.