How do you flirt with a friend?

keep eye contact a little longer than normal and sort of half smile
catch his eye from across the room and smile at him
touch him slightly on the arm when talking to him
sit or stand a little closer to him than usual

Honestly. I don't think I could be much of help.
i flirt with guys I would never give a chance too. (and I don't mean that in a mean way at all, I just mean I flirt with guys that I would never consider dating)
and I think its just simply because I'm a friendly person.
many girls are like me.
we try to be friendly, and our friendly way of showing our personality is by flirting.
and also, if I am talking to a guy I like...i seriously don't think I flirt as much. I think I mostly flirt with guys AROUND the guy I actually like.
i try not to do the whole OOO flirty routine where I laugh at everything he says and toss my hair. when I'm talking to the guy I like, I'm real. and I hope it shows.
which actually might give them the wrong impression that I'm sending a bad sign. but its the way I react without realizing...

When I flirt with someone I actually like, I try to do some more "serious flirting . " That way I can send hi signals that I like him instead of just friendly signals . If I was flirting with a guy friend I might touch him but if I was flirting with someone I like I would touch him, but my hand or leg or whatever would linger a little longer than it should . Same thing with eye contact . Eye contact is my favorite flirting technique because I am shy when it comes to boys so it is one I use often . When I flirt with someone I actually like my gaze would linger longer than it should and I might even smile if I am feeling brave . With a guy friend it would be easier to smile to him, but you can usually tell if it is a flirty smile or just a friendly smile . Hope I helped !