Virginia DeBolt writing on blogher.com has posted an interesting article “WordPress: Using the Image Gallery Feature” with a video, on how to create image galleries using built-in WordPress tools.
“The instructions emphasize several times that you should start a post, save it to draft, then insert the image gallery.
When you have the images selected and uploaded into WordPress, you add the very important alt text (and title text if you want it) using the Show/Hide options.”