Be tolerant of mistakes

If somebody makes a mistake of some sort or causes a screw-up, try to be tolerant and supportive. Chewing them out and dumping on them is rarely constructive, unless of course they do it all the time or the issue was the result of not really caring about the work. In the event of an honest mistake that happens once in a blue moon, the best response is to focus on cleaning up the mess. Pull the team together and do what's necessary to fix it; remember to pitch in yourself. Make people know that the team will support them to fix an error, because it's a fact of life that people make mistakes every now and then. Remember that it's only a question of time before you're the one who creates the problem and needs everyone's support to correct it.

After things are resolved, it's a good idea to try to figure out what went wrong (in a non-judgmental way) so that steps can be taken to avoid repeating the mistake. Unless there's some sort of ongoing problem with the individual...