Importing photos is a snap in iPhoto because the functionality is built into the OSX operating system.
Import from a camera or iPhone
By default, iPhoto should open automatically when you connect a camera. If it doesn't, select Preferences from the iPhoto menu. In the General settings, make sure that "Connecting Camera opens:" is set to iPhoto.
When a camera is connected, all the photos will be viewable in iPhoto. You can change the size of the thumbnail images to get a better look.
It helps to start with a rough edit to select which photos you want to import to iPhoto. The purpose here is to grab only the photos you might want to use and give your event a name. This will save you time and disk space. Control-click the photos you want to import and click the Import Selected button at the top right.
If you look in Events, your new event houses the new photos. If you want to combine photos into a single event, simply drag and drop photos onto the event you want to keep.
Import from email
If you are using the Mac's Mail app, click on the Save button in the header of an e-mail and select Save to iPhoto.
If you are using Web mail in the Safari browser, you can right-click or control-click on a photo in an email and select Add image to iPhoto Library.
Import from the desktop
You can upload individual photos or an entire folder by going to the File menu and selecting Import to Library. If you import an entire folder, your event will assume the name of the folder.