For editing I have a straightforward rate scale of 2-4 cents a word, based on whether the work is for proofreading, copy editing, or developmental editing. I can also convert my rate to an hourly one for work that is suited to this or for customers who prefer to charge by the hour.
I usually start by discussing with a client what editing services are needed. I find that authors have many different needs so we can talk about the rate before we get started.
For writing original content my normal rate is 7 cents a word.