There are 3 ways in asking a college girl out. Casually, socially, and formally. All are great options, and all can be used for one girl. College girls are usually looking to fill their schedules up and love meeting new people. I feel that in our 20s we all want some attention and new friendships. You can't be texting buddies forever! So, let me help you.
Asking a girl out casually will probably give you the best results if you want to build a true relationship with this girl, even if it ends up as a nice friendship. Casually saying to her, "let's study together this weekend" is adorable and demanding, but in a nice way. Other things like "let's go check out that new coffee shop tomorrow" are other casual ways to make the girl less pressured into saying yes. Casually asking a girl to hang out and spend time with you is the best way to get to know her, if you really want to. Just don't ask to Netflix & chill without chillin'.
If you're the shy type or think the girl will be shy, ask her to go out with you and your friends. It makes it easier for the girl to bring her girlfriends and meet up with you. Social hang outs during the day time gives you the whole day to hang out. So, plan a beach day, mini golfing, a day out in the city, etc. wherever your location may be! Being with a group of people lets you both see the social sides of each other because everyone is different when with their friends. Friends bring out true colors and it will make the time a lot more fun.
If you're more serious and want to keep chivalry alive, being a respectable guy never seems to fail unless the date actually fails. "I want to take you out to dinner" literally makes me melt. It shows me that the guy truly wants to spend boring quality time with me and it makes me think he wants to use this time to actually get to know me because we will be conversation the whole time. Guys who are respectable will make the college girl think that he is mature.