There are several ways to stay organized in iPhoto. One of the more common methods is by using various photo albums. Another, maybe less common, methods is by using Keywords. With Keywords, you are able to "tag" your photos with certain Keywords such as "family", "vacation", and so on.

First, we need to open the Keywords pane. To do this, click on the skeleton key icon in the bottom left-hand corner of iPhoto. A small window opens showing the predefined Keywords, as shown below:

These Keywords are predefined by iPhoto. To add or subtract from this list, go into iPhoto preferences (Command+comma), and click on Keywords.

Now that we have our custom list of Keywords, it's time to use them. To "tag" a photo with a Keyword, simply drag an image to the specified Keyword, and drop. The image below shows me tagging a photo with the Keyword "Kids".

Now that you have begun the tagging process, you can begin using the result. With the Keywords pane open still, simply click on a Keyword. If we clicked on "Kids", for example, all photos tagged with this Keyword would be displayed (while all others would be hidden). To show all photos again, click on the "Reset" button.

It may also be useful to see which photos are tagged with the various Keywords without having to click on each of the buttons. To do this, go to Show | Keywords (or press Shift+Commend+K). This will then show the Keywords assigned to each photo, as shown in the example below:

To reset a photo (to "de-tag" it), simply drag the photo to the button labelled "Reset".