Since I haven't played much as a spy (very sad, yes, I know), I'll tell you spy folks just what makes me notice you. I figure this can be helpful for spies and... not for spies.
A) This one's pretty much unavoidable, and if it happens you should curse. If I see two people with the same name. Yeah. If that happens, I know one of you is the spy. I tend to aim for the one doing nothing.
A2) This basically falls along the same line as A. If I see a class that we either don't have or somebody that's the same class as me (and I'm the only one doing it) and a quick Scoreboard check confirms it, the jig is up.
B) You don't do what you're supposed to do. What does that mean?
You're a Soldier, Heavy, or Scout sitting in a corner, waiting. In this case, you should have been a Pyro. A Demoman is passable, but then I'd expect stickybombs.
You're an Engineer and you're not building anything. Suspicious.
You're a Spy and you're not spying. Odd.
You're a Medic not Medicing. Medics are rewarded for constantly streaming health (even if everybody around is healed). Not to mention, all Medics should be out helping the damned offensive. Friggin' noobs. (And I'm talking about the Medics, there.)
You're a Sniper and you're paying more attention to me and my team than the other team. Have I made my point?
C) To tie right into that last one, if I notice anybody paying more attention to me or others on my team (especially if I'm a more-targeted class) than to what said disguise says they should be doing, the flag is raised. In other words, you need to PEEK at people while acting like you're doing something useful.
D) You rush straight toward your objective. If I'm an Engineer and I see somebody running towards me and my turret, I get very suspicious.
E) You're standing around somewhere strange and random. Nothing's happening there. There's no reason to be there. What the heck are you doing? 2Fort sewers, for instance. If I see anybody not actively moving forward or an Engi without a turret... Ahem.
F) You catch on fire.
A) This one's pretty much unavoidable, and if it happens you should curse. If I see two people with the same name. Yeah. If that happens, I know one of you is the spy. I tend to aim for the one doing nothing.
A2) This basically falls along the same line as A. If I see a class that we either don't have or somebody that's the same class as me (and I'm the only one doing it) and a quick Scoreboard check confirms it, the jig is up.
B) You don't do what you're supposed to do. What does that mean?
You're a Soldier, Heavy, or Scout sitting in a corner, waiting. In this case, you should have been a Pyro. A Demoman is passable, but then I'd expect stickybombs.
You're an Engineer and you're not building anything. Suspicious.
You're a Spy and you're not spying. Odd.
You're a Medic not Medicing. Medics are rewarded for constantly streaming health (even if everybody around is healed). Not to mention, all Medics should be out helping the damned offensive. Friggin' noobs. (And I'm talking about the Medics, there.)
You're a Sniper and you're paying more attention to me and my team than the other team. Have I made my point?
C) To tie right into that last one, if I notice anybody paying more attention to me or others on my team (especially if I'm a more-targeted class) than to what said disguise says they should be doing, the flag is raised. In other words, you need to PEEK at people while acting like you're doing something useful.
D) You rush straight toward your objective. If I'm an Engineer and I see somebody running towards me and my turret, I get very suspicious.
E) You're standing around somewhere strange and random. Nothing's happening there. There's no reason to be there. What the heck are you doing? 2Fort sewers, for instance. If I see anybody not actively moving forward or an Engi without a turret... Ahem.
F) You catch on fire.