I recently found a $100 savings bond that's 12 yrs old. Should I cash it or hold on to it? Don't really know how the bond works.

Check out TreasuryDirect (http://www.savingsbond.gov). Depending on what series it is, there could be a date when it stops earning interest. If you cash it, know that you will receive a 1099 for the interest that you will have to claim on your income tax.