Girls- Can you smell the BS from a guy when he approaches you?

I am intimidated and scared to approach girls cause of the misconception that since I am approaching all I want to to get into her pants. And its the opposite, well at least for me it is. So when or if I never do approach a girl its a genuine feeling, and truly for good intentions of just getting to know her and maybe a date. So can you tell if a guy who is approaching you is honest in those intentions, and then you can also smell the BS from the other guys who are trying to just get some for the night?