'Would being happy make me look attractive?'

I would like to be a happier person, because I think that my serious demeanour makes it hard for women to consider going out with me. Whenever I ask someone out on a date, they usually refuse because, according to my friends, I give off this vibe of being too serious. The thing is, I'm not a very serious person; I just come across as one. I think I laugh as much as most other people, so I don't know what they mean by this. I tend to overthink a lot of stuff, which is probably why I don't come across as fun-loving. What can I do to change this?

I'm not sure changing to fit some notion of what your friends believe is a 'fun-loving' persona is a wise thing, because you really ought to be able to date someone who wants to be with you specifically because of who you are. If you believe you come across as more serious than you would like to though, I suppose a few minor changes to the way you look or dress can do wonders. Speak to friends for some advice on how this can be done. I can't comment on how over-thinking stuff makes you seem more serious, because I don't know you personally, but I would advise you to not try and change who you are based on what other people think you should be.

Should I date a girl from my college because my friends think she is just perfect for me? I don't know her very well, so I'm not sure, but they think we would be perfect as a couple.

You haven't mentioned whether or not the girl in question wants to go out with you to begin with. Does she get to have a say in this at all, or have your friends spoken for her too? It's nice when two people get together, provided they have minds of their own and decide for themselves.