What do I need to do before I ask a girl out to be my gf?

Brush your teeth, take a shower, put on some clean clothes and then ask her if she'd like to go with you to dinner and a movie.

Complement her and be gentlemanly around her!!

Do I ask her to go on a few dates with me and then I ask her out?

Where I come from, the first time you ask a girl to go on a date, that constitutes "asking her out". If, after a few dates, you both want to continue, that is often called "going steady" or "getting serious", but these things are not generally arranged by means of questions or requests, except that eventually a proposal of marriage is possible.

Maybe you live in a very traditional society, in which case you should indicate which one, otherwise you are liable to get confusing answers from people e.g. in Western countries where the etiquette is much looser.

I live in the USA, I never had a gf before so I don't know, should I show her that I like her and see how she react?

should I ask her to be my gf directly?

I live in the USA, I never had a gf before so I don't know, should I show her that I like her and see how she react?

should I ask her to be my gf directly?

Usually people date for a while before it's determined if they will be girlfriend/boyfriend.

Have you gone out with the girl yet?