The first step in getting your manuscript into great shape is assessing your editing needs. Here is a rough breakdown of the basic levels of editing.
Developmental or project editing: Coordinating and editing a project from proposal or rough manuscript to final manuscript, incorporating input from authors or reviewers.
Rewriting: Creating a new manuscript or sections of a manuscript using content and research supplied by the author.
Revising (or substantive editing): Making substantive changes to the organization or argumentation in any section of a manuscript.
Copyediting: Editing grammar, usage, wording, spelling, punctuation, and style; checking for consistency in mechanics and for internal consistency of facts; ensuring conformity to style guides. This level of editing can run from heavy (more than 20 errors per page) to light (fewer than 10 errors per page).
Proofreading: Checking proofs of formatted, edited material for minor errors (e.g., in spelling or punctuation).