Here is my basic top ten list for taking great iPhone photos.
Tip 1: Charge your phone!
Tip 2: Clean your lens
Tip 3: Gather together your props (if food or product styling)
Tip 4: Find North with your phone compass (this allows for indirect light as your light source.)
Tip 5: Turn on your grid lines in your camera settings
Tip 6: Rule of thirds - use this to help with basic composition
Tip 7: Shoot in portrait mode on your camera settings
Tip 8: Try shooting at different angles to give interesting perspectives
Tip 9: Under expose your shot - this is easier to correct in editing that over exposing
Tip 10: Research photographers you like for inspiration and HAVE FUN with it.