Body language stuff... love catching them looking then shyly look down. When the kind of melt in a big hug or when I press them against a wall and kiss.

This is extremely difficult to answer. I suppose feeling a connection or chemistry. Looks are a secondary concern. Sexually, is a sense of being free and uninhibited with each other. Turn offs can be caused by simply bad atmosphere or timing. Hygiene is also important.

Not much turns me on anymore, but I will never get tired of looking. One who just never stops taking turns me off.