Often students will select books that are not at an appropriate reading level.  They may select books that are too easy in order to be able to read more books in less time.  This is alright once in awhile, but not on a regular basis.  Other times, students may select a book that is too difficult, because they like the subject matter or because of peer pressure.  Again this is alright occassionally, but not all of the time. 

The easiest way I have found to help students select books, is to use the Five Finger Rule:

1.  Select a page of text that contains an average amount for the book, a few sentences for primary levels and up to an entire page for intermediate levels.

2.  Have the student start reading the page aloud.  Each time they make an error or can't read a word, put up one finger.  (Do not count the minor mistakes such as "a" for "the", etc.)

3.  If they can complete the page with five or fewer errors, the book is probably an acceptable level for independent reading.