One
of the best decisions I made for my recent books was hiring a
professional editor--before I began submitting the manuscript for
publication. You might say: Why bother? The agent/publisher will make
you change stuff anyway. And don't publishers have editors?
Yes,
you'll have to change stuff--if you're lucky enough to get that far
with an agent or publisher. Yes, there are some publishers who still
offer editorial help to their writers (small presses usually do, partner
publishing does, a few big houses do if you're high on the list). But
it pays to invest in your own book in today's competitive world. Make
it the best it can be, before you try submitting it.