Restoring Your Credibilty, When You Just Look Guilty?

I was watching "Firewall" with Harrison Ford, (I think) today at the hairdresser. I say hairdresser to show that I wasn't paying the most attention. The premise should be that a suit and tie, Ford, is forced to rob his bank and wire the money to the mastermind who was holding Ford's character's family hostage. One of the details that made Ford's character a good scapegoat was his gambling debt. The bank that he held a high position at, would believe that he robbed the bank mostly due to his gambling debt as opposed to finding it to be weird behavior for an employee who presumably never stole from them before. 

This just showed me that integrity and character is so important. Two completely isolated incidents complimented one another so well, and not for a good look. This can be likened to a girl being labeled as easy by a date, even if she did not do anything with that date. Due to one past bad decision in a past relationship, the rumors add value, whether true or not, to who she is described as. Maybe this isn't the most eloquent analogy but you get the picture.

My question is, how do you restore your credibility when you may not have had a perfect record in the past? How do you clear your name from things you are not guilty of, but  past indiscretions show motive that match one another?