Try to focus on a simple way to ask for a date with someone. You need to be extremely confident about your attitude and intentions when it comes to asking a girl out. If you expect rejection way before you actually approach the girl then you will get rejection, try to keep a positive attitude when it comes to approaching the woman you're interested in, find out what her interests are, don't get nervous, anxious or depressed once you get a ‘no' as an answer. Try to make further efforts like being friends with her and getting to know more about her. Do not ask a girl out for a date over the phone, invite her in person, try to look into her eyes when asking her out she will see the sincerity in your eyes. Tell her how you feel about her, tell her if you feel she is attractive.
That may be the problem you try asking them out before getting to know them, maybe you should try getting to know her likes and dislikes before asking her out and maybe you will know if it's a good idea to ask her out or not.