Q. I am considering script consultants to look over my screenplay, and I noticed your services. Should one register their script with the WGA before sending it to any paid script consultants?
Q. Or, is this done after you have gotten notes and completed any changes you might make as a result of the notes?
No need to wait. No matter what changes you make to the script, it will likely retain many of the same characters, plot twists, scene order, chunks of dialog, etc., so that if someone poached a later draft, they would be using copyrighted material from the copyrighted draft.
Though, in general, very few people poach scripts. Really, very, very few.