Several tax credits can increase the amount of your refund. 

Earned Income Tax Credit: if you are a low-wage earner, this credit is quite important to you.

Child Tax Credit: if you have children who meet certain criteria, this credit can add thousands to your refund.  And if you do not receive the full amount of the Child Tax Credit, especially if you have more than 2 children, then you may qualify for the Additional Child Tax Credit.