So many times I am asked by coworkers and clients about the best way to keep up on the platforms and their ever-changing ways. The way to do it is through their blog.
Every major platform has a blog and they update it frequently with their updates and improvements. Below are the links. I suggest you add them to your favorites and check them regularly.
You can use these to learn and be the hero when updating clients.
#ProTip: many of them are Tumblr based. Use the +follow to have them show up in your Tumblr feed.
Twitter has many. This is the Advertising version.