I want to be specific about this because the advice most commonly given on this topic — vet carefully, check reviews, ask for samples — is accurate but not particularly actionable when you are sitting in front of a list of services that all look broadly similar from the outside. My experience using three different thesis editing and proofreading service providers before finally finding one I was genuinely satisfied with produced a clear enough picture of what actually differentiates them that I think sharing the specifics is more useful than repeating general advice.
