A solid way of at least kinda figuring out if something might be AI generated is the lighting. If it looks like super bright studio lighting, it's probably AI. It isn't a catch all, because some people will use studio lighting for "simple" photos, but it's good enough to get some idea.
You can also subscribe to and report things to bsky.app/profile/aimo... if you aren't sure, and the volunteers there will look at it and label it if necessary.
