The Sluff & Ruff
When I first did this page, I listed only the effective sluff & ruff. That was because it doesn't get all the much attention and when columnists trot one out, they act as if they'd just deciphered the Rosetta Stone, and I figured the S & R had enough bad press already. But I've come across some very costly examples of the other kind by people who should have known better, and so decided to include some of them.
The sluff and ruff has a not altogether unmerited odorous reputation among bridge players. Make no mistake about it: it can be a bonehead play, perhaps the one most likely to get your partner uptight. Nevertheless, if its reputation is not altogether unmerited, it's not altogether merited either. The sluff and ruff can at other times be a devastating play, and it behooves the aspiring player to take note of the times it would work to the benefit of the defense.
Indeed, I must beg to differ with the bridge writer who said a sluff and ruff "almost always" costs a trick. Such is its odorous reputation that you can't really find that many examples of it as a bonehead play. And conversely, examples of either a benign (neither costly nor helpful) or productive sluff & ruff aren't so terribly rare. The "majority" I would concede, but not "almost always". However, this is a pointless quibble, since the real crux of the issue is to avoid the costly ones and embrace the productive ones, insofar as we can.
So I would suggest the following: Give declarer a sluff and ruff only when you have a positive reason for doing so, only when by your view of the cards it will help the defense. You're allowed to be wrong. No one's infallible. But you should have a view by which the play will help. Otherwise, I would say simply do anything but offer your opponent a sluff and ruff. Your partner may have just the cards you need to make your other lead work.
The sluff and ruff won't cost you under these three circumstances:
1. Declarer has no more side-suit losers. If in addition to that, if declarer's trump is rather spotty, the sluff and ruff might constitute the most effective defense. At least you're getting something with your lead as opposed to tamely leading a suit where he has complete control; you're getting a trump.
2. The same holds when declarer has losers but cannot sluff one. A 4-4 side suit, headed by ace-empty in one hand, king-empty in the other and splitting 3-2 would be one example of this. Also K Q J opposite low-low-low. Declarer can only sluff a winner.
3. It won't hurt if all declarer's trump are already "busy", which is to say, are already slotted for a ruff from the other hand. See an example here.
The Benign or Productive Sluff and Ruff
Bonehead & Costly