Yes. Here they are!
More important than the amount of light in the room is the relationship between the light source and the subject. There should be a direct line between the light source and the subject.
Much like the previous tip, make sure that you're not blocking the light source when taking a photo. There are times when shadowing will not be visible to the naked eye but is visible in the photo. Always check the quality of the photo after taking it.
Try and keep your camera "flat" or parallel to the surface of the subject when taking photos. Don't hold the phone at angle as it will distort the photo.
Try and capture photos with a contrasting background to the skin tone of the subject. For light skin subject use a dark background and vise versa. Try and keep the background consistent. A matt finish on the background is also ideal.
This one is pretty obvious but still important to state. Hold the camera still when taking the photo! iPhones have good built in stability mechanisms however it is best to rest your phone/arm on something when taking a photo.
If you are taking photos to track progression or to comparing before and after shots, it is important that the photos be taken in the same position with the same light. Having a mark on the floor (for example) where you always take a photo from is a good idea.