The U.S. is home to an estimated 21 million college students. These students are usually thought to be young 20-somethings, but with today's ever-changing demographics, that market now encompasses adults between the ages of 18 and 30.

Reaching millennials, including college students, can be difficult due to the wide age range, often listed as between 18 and 34. Furthermore, not all college students are alike. While some may be teens fresh out of high school, others may have just returned to school in their early 20s, and some may even be parents.

One thing binding these...