Actually to get a girlfriend first thing first you must have character the girl that you want to be girlfriend. for example you want get a girlfriend who nice, smart, have long hair, good attitude, ext.
Second is you must become socialize to other people and have friends. Girl like man who have friends.
Third is you must become attractive to0. For example you must clean and perfumed.
Fourth is ask girl you want to meet to chat. If you want to know how to meet girl see this
Five is be confident that you can make her comfortable. This is important, girl want a guy beside her that make her comfortable.
Six is ask date. If you follow those step and confident that you can make her happy and want to know more about that girl ask her date.
Continue to deep identification each other.
If you feel comfortable with this girl and each other, you can ask her to be her boyfriend, and she become your girlfriend.