How do you let other guys know... "She's Mine"

if you're out with your girlfriend and you notice other guys hovering around her or watching her or even hitting on her(maybe even guys you know)

what body language would you use to let them know 'she's mine back off'?

or are you even conscious of the fact that you do it? (cause I see guys do a few things allll the time and I don't think they even realize it)

Girls~ what have you noticed your guy doing in these situations?
Updates
+1 y
one more thing...are you doing it on purpose cause I see shaun saying he does which is even better so if you do tell me :)
How do you let other guys know... "She's Mine"
Post Opinion