First, your own view pointThis is the viewpoint you had when you wrote the manuscript. Ask yourself: do the words say exactly what you meant to say? Sometimes the words that end up on the page are not the same as the words you had in our head. Read the text carefully. Are you quite sure this is what you meant to write? When you wrote, Jane leapt at the opportunity of a new job, did you mean that she physically leapt into the air? Or did you mean that she took the opportunity joyfully? When you wrote, Tom saw the mess his dog had made and realized he’d put his foot in it, is that really what you meant?
Secondly, your main character’s viewpointThis is particularly important when you write in a first person singular viewpoint. The words should reflect what your main character was thinking. Those words came from you but you are not your main character, however much you might like to be. Your character will think and act differently to you, and that must be reflected in the manuscript. Try once again to see inside your character’s mindset to see if your written words really do reflect his or her thoughts… not yours.
Thirdly, the reader’s viewpointThis is the really important one. Can your reader enjoy the book because you have chopped out or corrected anything remotely confusing? You know what you meant when you tapped out those words, but now you must ask yourself if your readers will actually get it.