If consolidation or refinancing is not a feasible option for you then I would recommend focusing on high interest rate loans first. Paying down the principle on those will enable you to avoid high interest payments, even if the balance is lower than your other loans. For example, if you have two loans, one with a balance of $11,000 and an interest rate of 3.2% and another with a balance of $4,000 and an interest rate of 5.6%, it would make sense to pay off the $4,000/5.6% loan first since it will accrue interest faster than the $11,000/3.2% loan.
Kristin made a good point about checking for early payment penalties - understanding the terms of your loans is critical to prevent extra fees.
I hope this helps - good luck!