If you were under the age of 24 at year end then the key requirement that you need to answer is whether or not you provided more than half your own support for the entire year. If you did, then your parents can't claim you as a dependent. Keep in mind that support also includes the value of rent and utilities that your parents probably pay for. There is a worksheet on p. 16 of IRS Pub. 501 to help you determine the support answer: http://www.irs.gov/pub/irs-pdf/p501.pdf
Here is a more complete list of the tests you must meet to be claimed as a qualifying child by your parents:
1. The child must be your son, daughter, stepchild, foster chld, brother, sister, half brother, half sister, stepbrother, stepsister, or a descendant of any of them.
2. The child must be (a) under age 19 at the end of the year, (b) under age 24 at the end of the year and a full-time student, or (c) any age and permanently and totally disabled.
3. The child must have lived with you for more than half of the year. Temporary absences while away at college are considered living with you.
4. The child must not have provided more than half of his or her own support for the year.
5. If the child meets the rules to be a qualifying child of more than one person, you must be the person entitled to claim the child as a qualifying child.
6. The child must be a U.S. citizen or U.S., Canada or Mexico resident for some portion of the year.
7. The child must be younger than you (or your spouse, if filing jointly) unless disabled.
