This is by far the most important suggestion of all. The rules for taking a good picture don't change when you switch between cameras. Just because the camera can also make calls, doesn't mean you should ignore everything you know about balanced composition and expressive lighting. If you need to keep the rule of thirds or golden ratio layover on your screen at all times to help remind you, certainly turn it on.

 

While the tips I've outlined here will help you maximize the strengths and minimize weaknesses of a smartphone camera, it's ultimately your skill, knowledge, and eye that will make photos worth looking at.