Jane, you have to decide what it is you want to learn. Small bits are fine if you trying to learn a lot of ideas that you will later synthesize into your own. But maybe it is time for you to choose to learn a whole song as well to help you feel like you are accomplishing something.
There are lots of books I could recommend. I especially like Warner Bros. 21st Century Guitar: Method, Rock Shop, and Song Trax all with levels 1,2, &3. It is available on Amazon if you have trouble finding it locally.
For great free lessons of all levels, try
http://www.guitarnoise.com/index.php
Best Wishes!