House rules for Spade bids of nil, blind-nil, and 10-for-2?
The main rule I strongly endorse is that you only trade ONE card, on blind-nil bids only.  No trading cards in any other situation - the only purpose is to avoid the "oops, guy going blind nil has the Ace of Spades" case which makes the whole round more or less pointless.

Other than that I have also frequently played with a "must be X points behind" rule on blind nil.  Is it really happening (successfully) so often that it overshadows all else?