If a guy is annoyed by you he will try to avoid you. It's as simple as that. I'm not sure why the other guy that answered tried to make it so complicated lol. If a girl annoys me my responses when she talks to me will be as few words as possible and I will leave her presence ASAP.
They'll act serious with you and won't be so talktative. Sometimes they'll even pretend to be busy with something to get you to stop talking to them.
But here's a tip for you - if you don't think you have done anything wrong or annoying to the guy, and he still keeps on being like this, don't keep on trying. Give up and move out. Some guys aren't worth your time, and there's no point in trying way too hard to getting ONE guy to like you, if he doesn't seem to be into you.