It just takes exposure to different varieties and experience(time) to begin identifying them. Some differences are subtle and some are extreme. It also is often easier to tell what a banana is not rather than what it is. There are just so many cultivars, many uncommon and not yet named. I'm not sure about good books for identification but I don't think you'll find any websites better than this one. Check out
the Wiki and the
Photo Gallery. Use the search engines in them to search for a certain type and then study the information and pictures to learn about that particular variety. You will learn about common traits and which bananas have which traits and which ones don't. Then if you have a certain question that is still unanswered about a variety like
"Do 'Basjoo's have a waxy(glaucous) coating on the pseudostem?" or
"do young 'Ice Cream's have red spots on the leaves like 'Cavendish' do?" just ask in the forum. You'll get answers and learn more about bananas as you go. Before you know it you'll be helping people figure out what they have... or don't have.
