"Some girls"? What does that mean?
All I can tell you is getting a date is all about finding success after often long strings of failures. How do you go about asking?
My suggestion is to date without making it look like a date-date. Get acquainted with a girl. Any available girl. Find out if there's a place she likes to eat lunch. Offer to buy her lunch or something. Or if she likes to go bowling, offer to take her bowling. You're not "on a date." Because a "date" implies an expectation she may not be ready for. It's all in the mind. You really are on a date, but you have to think about it with a different mindset.
Because you're getting dates at this point without the express intention of it becoming a relationship, you're free to go out with as many girls within a given time frame as you can manage. You can take one girl to the zoo on Saturday morning, do lunch, take her home and then chill on your own for the afternoon. Pick up girl #2, take her rollerskating, grab a pizza, and top the evening off with a movie. Take her home, then reward yourself with a beer.
Don't worry about getting a gf. Don't initiate any physical contact. Respect boundaries until she breaks them first. Keep it friendly and more girls will likely be ok going out with you.
What will eventually happen is that some girls will hang out with you more than others. Some girls are naturally just affectionate towards everyone, so don't let that get your hopes up early on. But if it turns into an ongoing thing, THEN you have a gf and it's a good idea to stop hanging out with other girls. Take the physical part of the relationship to the next level, only a little bit at a time.
See, what I think is going on with you is that you don't socialize enough with women for them to feel safe around you, and I'm worried that because you're maybe being too direct in seeking a gf. We've had this discussion before. Just slow down is all. Go for bulk and get acquainted with women. The gf will happen when it's time.