Every writer wants to avoid continuity errors, or at least I hope that is the case. I definitely do, and it's one of the reasons I have a whole bunch of people proofread my books, preferable people who have read earlier parts.
Even so, continuity errors can be missed even by them, and small ones can creep into writing through successive edits. A while ago, when working on the first five Unbound books, my editor mentioned a technique she used to spot them, and I've since adopted it to spot possible errors as soon as possible.
Read your book backwards
It's that simple! Start with the last line in your book, and read it. Then continue to the second to last sentence, then the one before that, until you've read the entire book backwards. I've just finished doing this for Incursion
, and I corrected 7 continuity errors as a result.
It takes a bit of discipline to keep reading in this order, and I've found that it's easier to reverse the entire file before I begin, so I can read it top down and still get it in reverse.
A word of warning however, reading a book backwards takes quite a bit of energy and concentration, and I find I get tired rather quickly when I do it. Don't try this unless you've had plenty of sleep (or a few gallons of coffee or Red Bull).