I'm actually good at spotting fake faces. It's not that difficult if you know how, although sometimes they are convincing.
1. If you can't tell what is going on with the background, it's fake.
2. Look at the hair. The AI is bad at recreating hair and will often leave strange artifacts around or attempt to recreate hair strands that look surreal.
3. Look at any distinctive element like glasses, ornaments, etc. The AI will often attempt to add elements like glasses and ornaments, but they will look strange. Glasses might look "smudgy" sometimes, specially the temples.
4. Look at the clothes. They will most likely also look "smudgy" or have artifacts.
5. Check if the lighting also matches.
Look at this face. It's very convincing, right? But if you check closely, you will notice how the hair and the temples of the glasses look blurry, with some artifacts at the right part of the hair. If you look at the clothes, specially at the neck of the shirt, you will notice that the geometry of the neck at the right part of the image does not match how the neck of a shirt should be.