The best way to keep your brand reputation high is to learn from your mistakes and try not to make them again. You can also try to learn from other’s failures, but you will probably never avoid the slips completely. That is why it is also important to find out how a brand should act after they make a mistake.
The first step is to make sure that you are open to criticism and will be able to notice when you fail. Then your first step should be to apologise and try to make up for your mistakes. You can, for example, send gifts to people that were affectioned by your misbehaviours or give them a discount.
But the best way is to be creative, just like Boeing was after they sent a cold, formal rejection letter to a child’s plane design proposal. They then apologised formally on their social media and invited the kid for a tour around their facilities.