In dungeons or trials (pf or df) I'll inspect everyone I don't know to get an idea what kind of run we have, or if I have to slow down (I mostly tank stuff, so if I see someone is undergeared I know I have to take it a little slower. Sometimes)

In the overworld...I try not to stare (click on them, examine, quickly target something else or untarget) since it is a bit rude to,especially if I don't know the guy I'm examining. Certain people I will sometimes just target and somewhat afk just to get a reaction :P