We said something similar in a previous post: order matters, and as you begin the editing process, you’ll save yourself time and endless frustration if you keep this order in mind:
Big-picture —> Paragraph level —> Sentence level —> Word level
If it helps, try thinking of the editing continuum as something similar to the order of operations in arithmetic. If you perform addition and subtraction before addressing division and multiplication, you’ll end up with a meaningless jumble. Similarly, if you attend to spelling and punctuation or dialogue and characterization before you’ve resolved issues in the plot, your results will be disappointing at best.