Gmail revolutionized online email clients when it first launched, and has since added a host of functionality and features to the site to help users get trough the ever-increasing number of emails they receive every day. But many of those features aren't even known by most, let alone used, so the Gmail team has set out to create some tips for all types of Gmail users, from rookies to seasoned veterans.

“Everybody has their own system for managing email, but some are definitely more efficient than others. Even if you only get a few messages a day, there are probably some simple things you can do to make it easier to get through your inbox and maybe even have a little fun along the way.” Zach Yeskel, product marketing manager, wrote on the Gmail blog.

“We know time is valuable, so we asked lots of Googlers for their tips and tricks on how they make the most of Gmail, and we combined the best of these into a guide at www.gmail.com/tips, cheekily entitled 'Become a Gmail Ninja.' The tips are categorized into ninja belts (white, green, black and master) based on how much mail you get each day.”

The four categories are based on user experience and, while the first two may only be useful to those just starting out or who rarely use it, the last categories have some really advanced stuff that even the most experienced Gmail user may not be aware of. And, if you're really into learning more about Gmail, Google has made available a PDF version of the guides, for you to print out. There is even a laminated version you can buy, and Google offered 1,024 of them for free, but they have since run out.