CAD Tools is a powerful plugin for QGIS that is intended to improve your digitizing workflow. While it has a lot to offer, the tools are not very self-explanatory – especially for people who are not used to the CAD way of doing things.
Luckily, there is a great learning resource out there. Stefan Ziegler explains the tools and shows their use in a series of screen casts that are easy to follow and reproduce. Enjoy!