By tagging pictures with ratings, you can find all your five-star pictures to show off your photography skills to your friends.
For more flexibility in tagging and sorting pictures by keyword, make up your own keywords and tag a picture with multiple keywords so you can find it in different ways. For example, use keywords that evoke specific emotions, such as Happy, Freedom, or Melancholy. Then tag pictures using keywords that describe specific events or places, such as Reunion (to identify pictures involved with family reunions) or Europe (to identify pictures taken in Europe). By using multiple keywords for each picture, you'll always have multiple ways to find your pictures again—whether you want an image that evokes a certain emotion, captures a certain event, or shows a certain area or place.
Half of the fun of digital photography is the freedom to take pictures and keep only the good images. The other half of the fun is using iPhoto to organize and sort your pictures so you'll always be able to find them again.