What to do if a guy (who is a player) seems really sweet at first but then looks for getting "one thing"?

There's this guy at my school, who has never spoken to me ever until now while im waiting for myself to take the state exams, i have this really instictive gut feeling that something about him at first was definitely not right, and then when i soon heard and realized what kind of person he really was well then it made me come to think that judging a player doesnt neccesarly mean they are bad people, they just have issues with dealing or commiting to just one thing, and so i decided that maybe just being "friends or distant" friends would be better than just ignoring them completely, and a person told myself they seem very sweet at first but then later on they get mean and rude, and start getting all hormonal and everything, and so i dont know exactly what to do?