The regular chatting with a writer is very important as you are able to control the writing process in this way. Ideally, such a service should have a real-time chat for customers and writers. So, make sure of it in advance.
Some have opined that students go for these services because they are lazy. This is partly true, but the biggest percentage that goes for these services are students who are trying to beat serious deadlines or have a deficit in their writing skills.
You might think that custom writing started with the internet, but did it? If you go down history, custom writing started back in ancient times before the invention of the written word.
Remember that if you go for a cheap essay writing service, plagiarism risk is very high. You have no way of ascertaining that you have received original work without running it through a plagiarism detecting software. To ensure your work is original, the online writing company should provide a free plagiarism report. This should be included in their service guarantee.
Most probably, you know friends who have used pre-written essays. These are in a better position to advise you on the best services available. Ask them their experience with some of the services you think of contacting. Get views from different friends to determine the most appropriate service for you.