How to subtly arouse a guy?

ok there's this guy friend of mine and we constantly flirt. our group sometimes does movien night/sleepovers but we're not alone :( sooo in the presence of other friends without them noticing and being too obvious how can i tease him and let him get the hint to have ? don't suggest low cut shirts (they don't work anymore lol ) and don't call me a slut... just answer my question :) we're all 19-20