Most Helpful Guy
Just have fun all the time, do not be mean, inconsiderate, or a jerk when teasing them. If it is about something you know she is self conscious about then it is off limit.
Be direct and ask them out making it clear it is a date. If they have given you their number or contact info they already know your interested and are expecting it. It will not bother them.
To keep you from worrying about what your doing/saying, and from what they are thinking - do not care about the result (You will become more attractive because the way you act towards them won't be all the wrong ways that helps kill the attraction.). You will learn what you are doing right, and what you are doing wrong and can make adjustments. You will learn when they are not being receptive and you can remove yourself before they can even reject you and you will be excluding them yourself before you know it. You will learn when there is no chance they will shoot you down. When you do not care and do not expect anything it makes everything so much easier for you.
Be yourself, have fun, be direct, and do not care about the result.1THIS IS NOT RELEVANT ANYMORE