根据YUI3 Team 的推荐，应该按照以下支线进行学习。

Getting Started

1. Check out the examples of YUI in action. We recommend starting with the base YUI module and then move on to Node. Other utilities like Event, IO and Drag and Drop make for good points of exploration.
2. Remember that there are full user's guides for each component on the YUI website. If you have any questions about a component as you play with the examples, check out the component's user's guide (by following any of the links along the left side of the page) or the searchable API documentation.
3. Start building. Use the YUI 3 Configurator to configure a page for YUI 3 usage or base your exploration off of one of the existing examples.
4. Become a member of the YUI community. The YUI team and developers in the YUI community share thoughts and solutions in YUI 3 Forums. YUI developers also contribute to the YUIBlog, where you'll find in-depth articles, videos and other great content about YUI and the world of frontend engineering.

顺便插个图，测试一下Live Writer直接插入图片的效果。