Skills in profiles

I was curious to find out what ideas people have about the skills in the profiles.

When do you think people should check a skill in their profile--when they know the fundamentals...when they can do anything routine...when they can do something most people can't?

If you've checked a skill, how did you decide when to do it? Did you just feel you were ready...did you set a goal of completing some project...did you have someone else evaluate you?