Do I file a tax return if I only made 8000 gross income and I'm single and 21 years old?

You're not required to file a return for your Single filing status if your 2008 income is less than $8,950 (or less than $9,350 for 2009). Even though you're not required to file, you should file if income tax was withheld from your earnings in order to receive a refund of that tax. Also, if you're eligible for certain credits (such as earned income), you should file even when not required