wat goes on inside a guys head, when he likes a girl?

It depends on how old he is and what it is that he likes about the girl, and also it depends a lot on the dress and actions of the girl. Girls must remember that they have control of what a guy thinks about her.

You can't always control what the guy is thinking
And sad part about boys is they do think about sex a lot
Not always in a wroung way things just remind them of sex ofter my man is very open and tells me these kind of things happen
But if you show a lot of skin then yeah there going to think about you like that
If you don't then well you don't
There are guys out there that are full of respect and others not so much