Brandon, It's usually just the flapper valve in the tank or the chain associated with it that causes you the problem. It's an easy fix and the flapper valve will have replacement instructions on the packaging. There are very few different styles of these and, with the exception of a specific one for some Kohler toilets, almost all the rest of the toilets use the same flapper.
If it has been a long time since you changed out the toilet internals, or it looks like it has been a long time since that, you might consider changing out the whole "works" from inside the toilet tank. It's not that much more of a job and actually pretty easy. Again, pretty good instructions are usually on the packaging and the parts can be obtained from any home center.