The first thing to do is to get whatever card you can, preferably one without an annual fee.

I'm a 21 year old college student as well, however I got a free/no benefit Wells Fargo card when I turned 18. When I turned 19, I applied for the Amex HHonors card(free one) and was approved with a $2000 credit limit. Now, two years later it has been upped to $5000. I also applied for the AA 75K Citi card a year ago for the promo and was approved for that with a $4000 limit. I also have a Cabelas Visa card which I received about 1.5 years ago with a $3500 limit.

Long story short, it can be done as a young person/college student. Ironically, one of the community colleges I took classes at charged a fee to pay tuition off through an electronic funds transfer but no fee for paying with a credit card! Easy points. I however was working two jobs most of the time until recently along with not taking out any student loans. I paid off my tuition as it came. Both of those aspects probably helped me get to my current situation.

Building my credit however has proven more than worthwhile as I just recently purchased a home and was approved for a mortgage at the age of 21. Likely thanks to all of my credit cards.