You may claim either a tuition credit or deduction. The most generous tuition credit (American Opportunity Credit) is a dollar for dollar credit on the first $2000 of tuition paid, 40% of which is refundable (you get it even if you don't have a tax liability). The maximum refundable part is $1000.
The 2nd credit (Lifetime Learning Credit) is 20% of what you paid (up to $10,000) and is non refundable (it only reduces the tax owed).
The 3rd benefit is an actual tuition deduction (Tuition and Fees Deduction). It only reduces your income (up to $4000) before tax is calculated. For most people, it's worth 12% of the deduction, in reduced tax.