have i ever been in situation? Well there was this one time.... uh
Act the same way you normally do. If you notice one is coming to ask you things about the same subject and it becomes a bit predictable try saying something to the effect of "You ask me about that a lot." before you give them a normal response.
And if one is staring at you, and you get bothered by it, try looking back at them for a moment, pretend to go back to what you're doing and then look slowly back as if you were suspicious of being watched. If they were looking at you they'll probably notice that you're noticing them staring and they would probably stop. If they were looking at something behind you they might not.