A lot of scholars feel that they need help with their english writing and it is not a bad idea to look for a reputed proofreader for your work. Whether your supervisorr has suggested you one or you yourself feel the need to improvise your work with somexternal help, choosing the right person can sometimes be perplexing.
The first thing is to be careful as all the proofreaders want to make money and there is are a lot of good and bad companies out there. Being cautious as much as possible before finalising is always better.
Quite often supervisors advice their students to go for an external proofreader even before they see the work. Universities have their own policies about proofreading. Have all that you are seeking from proofreasing written down so that pass over the same clarity that you have about your expectations from the proofreader.
The next thing to do is to check out the credentials of the proofreader by going in the details of his training and background. The qualifications, experience and expertise of the proofreader must be verified and examined thoroughky before assigning your work to him. It is always better if you proofreader has a degree, experience in your subject area, the native speaker of english language to be thorough with the naunces of the grammar.
Whatever commitment the proofreader makes, check and ensure that they do all of that. Somethings that you can check before hand only are, whether they would be using track mode changes, coaching about the changes and so on. You can get some assurance and help through references and testimonials that usually are promoted through the company website or even better if you can do it through some informal source of yours for more genuinity. Sometimes the company fabricates testimonials on their site from unreal people, be cautious of it.
The rates quoted by proofreading companies need to be compared and matched with their efficiency and expertise over which you have evaluated and understood them.
Lastly, if you are giving your work to a company, try to know the indivuidual person who is going to be assigned to do your work. A company may have many prrofreaders working for them and if you are looking for a long association with the proofreaders for a lot of work them it is always rewarding to work with one of them throughout the course.