For any tool that starts from your photo rather than a prompt, the source image sets the ceiling. No model recovers detail that was never captured, and a soft, dim, heavily compressed photo produces a soft, dim result.
Light beats megapixels
A well-lit photo from an ordinary phone outperforms a dark one from an expensive camera. Face the light rather than standing with it behind you, and avoid harsh overhead light, which drops shadows into the eye sockets and under the nose.
Keep the subject sharp and unobstructed
Motion blur and heavy compression can't be undone. For anything involving a face, that means no sunglasses, nothing across the mouth, and the whole head in frame. For products, get the full item in shot without a hand or price tag covering part of it.
Give it room
Photos cropped tight to the subject leave nothing to work with when a tool needs to reframe or extend the scene. A little space around the subject gives better results than a crop that clips the edges.
Vary the set
Where a tool accepts several photos, near-identical ones add little. Different angles, expressions and lighting conditions describe the subject more completely than five versions of the same shot.
Start from the original
Use the original file rather than a screenshot of it, or a copy that has been through a messaging app. Each re-encode strips detail before the model ever sees the image.
