In addition to any education benefits provided by the Post 9-11 GI Bill veterans are also able to access federal aid in the form of Pell Grants and Stafford Loans (that typically have low interest rates). No matter how many benefits you are eligible for through the GI Bill, you should make sure you are able to access financial aid to cover any extra expenses.
In order to receive financial aid from the government, you'll need to fill out the FAFSA every year you are in school.
When you do submit the FAFSA, make sure you list any other education benefits you receive as resources, not as income. Listing benefits as income could drastically alter your resulting financial aid profile.
Also make sure to submit the FAFSA on time (check the deadlines listed at your school), and make sure all of your information is accurate. If you have a change of circumstance, or a financial issue that you weren't able to report on the FAFSA get in contact with a Financial Aid Administrator at the college. This is the person who will be able to make adjustments to your financial aid profile and get you more help if you need it.
Don't forget to consider scholarships and other grants as well. You have just as many financial options to fund your education as other students, and more!
Get an estimate of your benefits.