I usually wouldn't show a hand voluntarily against good and thinking players as they don't need any free information.
A case can be made for showing to enhance an image and set up future plays.
For instance, when everyone folds to your standard raise and you show AA so they think you're playing tight, when you are really opening much wider but happened to have it that time.
You don't give much away since most will assume your raising range includes AA.
Seen a few CardPlayer articles on the topic so there is some good stuff out there.
Good luck to you!