Yes, that's what I always do before making captures (also, creating the page with the IMDb number if the movie/series is not listed yet allows to sometimes find it listed with a typo in the title :D)
You can't "reserve" a recent movie for months/weeks in advance, but for older stuff it is less a problem (less risk that someone can do it before you), and it can be justified if that covers the time before getting the DVD etc.