Editing is a multiphase endeavor. From rewriting lines,. paragraphs, and entire chapters to checking for punctuation and misspelled words. It seems no matter how many times I go through a manuscript, I always find something I missed, along with others who have also gone over it.
How do we miss so many items when we've read every single word many times over? The answer is actually in the question. When we've read page after page our brain has taken a snapshot of the pages and fills in the common words as we read. Each time our eyes fly over the written words we, by nature, skip some, our brain having alread assumed they were there.
A trick I read about some time ago seems to work - most of the time. If we read each individual word right to left, instead of our normal way of reading rigleft to right, we will find the errors. Why? Because our brain has been trained to read a certain way and this process is interrupted when we change the pattern.
Try it some time. I know it takes a lot of time, but when we send out our writing it has to be the best we can make it and typos should not be part of our presentation of all our work. Although, many books I read from well-known authors have many typos. And this is after a highly trained editor has gone over the manuscript.
Oh well, I guess even the best of us miss once in a while.
Good writing and let me know if this works for you.