Before asking a girl out on a date, start a casual conversation between the two of you to decipher if there are any sparks of chemistry. If she likes you, she will keep the conversation going, so have several topics in mind. Once she feels comfortable with you, casually ask her to join you on a date but have a specific outing planned with all the details worked out so she knows what she is agreeing to.
Start a casual conversation with the girl you like in person. While you can chat with her via social media or text messaging, talking to her in person allows you to watch her cues and gauge her interest. Ask her questions to help you get to know her, such as what the most spontaneous thing she's ever done is or what musical group she would pay the most money to see live in concert.
Pay attention to her verbal and non-verbal cues. If she continues the conversation and reciprocates by asking questions about you or laughs at one of your jokes, she probably likes you or is open to getting to know you. If both of you are laughing and talking at the bar and she casually offers you a sip of her drink, she is signalling she is comfortable with you and likes you.
Ask her out in person as this shows confidence versus embarrassed shyness if you message her via social media.
Develop a plan for when you ask her out, such as attending a local concert in the park that weekend and grabbing a pizza afterward. Make it sound like you are going to attend anyway and invite her to join you. Give her plenty of notice, at least five or six days so she can change her schedule if she has plans.
Remember if she has legitimate plans the first time you ask her out, try again another time. If she likes you, she will adjust them soon.