The way it worked for me was that I was familiar (but not good) with common lisp. So, to get me going, using CLTL[1] as reference, I watched the videos first. Its about 20-24 hours worth of watching. Following this I started reading the book and implementing the exercises and the projects in the chapters (register machine, logic programming etc.) in Common Lisp. That required me to understand the concepts well enough to port the scheme stuff to common lisp. This way I ended up learning Common Lisp with a decent grasp of Scheme.

Note that common lisp comes with a lot of stuff built in, but to do the above I stuck to a minimal subset.

Following this, it was fun to read OnLisp[2].

[1] http://www.ida.liu.se/imported/cltl/cltl2.html

[2] http://www.paulgraham.com/onlisp.html