Well i wouldn't say i'm an expert but if i'm flirting i'm normally pretty subtle, touchy feely, try to hold eye contact. I don't really know about eye contact, but when someone i think is cute looks me in the eye i look for a sec then look somewhere else, so maybe if they don't hold eye contact well they have some form of feeling toward you, kind of guilt at liking you but of course in a good nervous way. Smiles i'd say are the best sign, i smile a lot when i'm flirting. But in my small experience of 1 boyfriend at 14 (sounds immature but whatever, 2 yrs ago ish) he was very touchy because for some weird reason at my age 16 you can get away with hugging a guy or grabbing his ass, there's this weird social thing going around how guys keep feeling eachother up, but i swear their straight. But anyway, better stop talking lol.