5.) Avoid using digital zoom
Whilst the majority of phone cameras have zoom capability, it's best to avoid this when taking images unless it's a true optical zoom (where the scene is enlarged by the moving elements of the lens). The zoom on most phone cameras isn't an optical zoom, rather a digital zoom, where the image is artificially enlarged from the original scene by interpolation (increasing the true size of the image) and cropping. This results in a blurry, undefined and pixellated image.
However, some newer models do now offer a true optical zoom, such as the iPhoneX and Pixel 4. Check out your phone's manual to see what it is capable of!