One of the most highly recommended ways to increase your tax refund is to increase your contributions to your retirement fund. Contributing to an Individual Retirement Account (IRA) not only facilitates saving for retirement, but placing money into the IRA lowers the total taxable income because it comes off the top. The more you contribute to the IRA, the less of your income is subject to taxes. Generally, the lower your taxable income, the less you'll owe in taxes, and the less you owe in taxes, the greater the refund.
Be careful, though, to make the IRA contribution by the deadline, and know your limits. There's a maximum amount that can be applied for lowering taxable income. Consult a tax professional to ensure your IRA contributions are made on time and in the right dollar amount.