You write to communicate to the hearts and minds of others what’s burning inside you. And we edit to let the fire show through the smoke.Arthur Plotnik
As an author, you have a vision. You know what you want to write, and with whom you want to communicate. You also want to make sure you have accomplished this well. An editor acts as a second pair of eyes and works with you toward that goal.
If your collaboration is a successful one, by the time it is finished it can feel as if the project was something of a partnership rather than just a solo effort with a bit of outsourced language checking. The best partnerships are those that produce something better than each person could on their own.
You need to feel comfortable with the editor you choose. If there is a good rapport, it is likely the collaboration will be successful. No matter how technically proficient someone may be at their job, I believe it is at least as important to find somebody with whom there is a natural synergy. Because the end result will reflect the positivity of the process that went into creating it.