Here's 100 tips and tools for managing your library.
Personally, I don't like big libraries a great deal. I think there's something a little obscene about every pastor owning thousands and thousands of dollars of books that he has only read once and then chucked on is shelf, and then urging all his congregation to buy lots and lots of books that they read once (if at all) and then chuck on the shelf.
An exception to this is reference books, and those which are such classics they will get the re-read.
I'm a big believer in borrowing books and using libraries. Perhaps a pastors should buy book, and donate them to a local Christian library. That way they are investing in a new area. Then when they move to a new place, they have less stuff to move with them and they can start again at building up the local Christian library.