Can anyone help me?!?!?! preferably teenage guys...?

everytime i like a guy and we start to talk i NEVER act like i like him (flirting, ect.). how do i change that soo that i can show guys that i am interested. what do guys like girls to do when they like them? what do u want us to do when we flirt that makes u no we r interest in u (hair twirl, bite lip, ect.)?