The Daily AutoCAD blog routinely offers tips for drafting that are useful for starting and intermediate drafters. While there are often lisp programs, there are entries about drawing inclined lines and filleting corners as well.
Todays blog talked about using mirror to create a centerline mark. I think mirror is a command that is often under used because people don't think about how to fully utilize it.
When I used to teach drafting one of the challenges I would set forth was to draft an object (say a flat) using the fewest number of commands. While using mirror to copy and rotate the 2nd center line may not make you a 100% faster, thinking about how you use basic commands more efficiently on a global scale can make your drafting quicker and more accurate.