I would suggest finding a javascript framework and learning how to use it. Then you can see practical applications to how javascript works in real life. It will give you practical applications, and a much more specific (and larger) set of answers to "how to I..." type problems.
jQuery is a good framework to begin with, YUI and/or Prototype are good if you really want to dig in -- those two are meant for building your own resources, whereas jQuery is more focused on being easily usable.
Modern javascript is heavily about "prototyping" javascript to build in new functionality that's not included in its implemented specification. In other words, it moves beyond the basics of how to code in javascript found in most books and into the realm of "how to make javascript do more than it was intended to do." But the basics are a must if you intend on prototyping the language.
If you want to learn javascript purely for servicing clients and making better websites, then it really depends on how you learn. Personally, I learn more through practical application than just reading and exercises. If you're the same, then I suggest reading through (not working through) your book and meanwhile do a lot of reading up. I suggest "yui vs. prototype vs. jquery" as a starting Google search.
Think up a simple project you'd like to do, and then try and implement as many cool javascript features into that project as you can (ajax form submissions, automatically updating graphics based on form selections, image zoom, and animated fade effects some to mind as the most practically useful).
Again, it really depends on what your goals are -- do you want to become a contributor to a framework like jQuery, write plugins, or just know enough to implement functional javascript on a client website and look good on a resume. If it's the latter -- pick a framework, learn it. jQuery is the most user-friendly, Prototype is the most functional, YUI is as functional as Prototype, well supported, and a great up-and-comer.
