(i) Loud = penalties/confident, rising inflection = take-out/tentative.
(ii) For the more sophisticated player: reverse (i).
(iii) Agree a comprehensive set of rules, and agree it with your partner. It is better to have a bad agreement than no agreement at all.
The advantage of (i) and (ii) is that no further discussion is required. Below is one, but by no means the only, playable set of partnership agreements if you embark upon (iii):
Unless the situation fits one of the categories below, double is for take-out. Of course, the higher the level of the double, the more likely responder is to pass for penalties. Take-out doubles over 4S and above tend to have the meaning 'Bid if you have some shape or primary support, otherwise pass and hope to beat them in high card strength'. At lower levels, responder should be reluctant to pass without a trump holding. The following doubles are all for take-out:
(a) 1S Pass 3S Dbl
(b) 1S Dbl 4S Pass
(c) 2C* Pass 2D* Dbl (2C = 8 tricks, any suit; 2D = relay.)
(d) 1D 2C Pass 4C Dbl
(e) 1H 2H Pass 3S (2H = Michaels, 5/5 spades and a minor.)
(f) 1S 2D 3S Dbl
(g) 1S Dbl 4S Dbl
(h) 3H Pass 5H Dbl
(i) 1H 1S 2D Dbl (Double shows cards, clubs and spade tolerace.)
(j) 1NT 2H Dbl (The take-out double here shows at least two hearts and the values for 2NT.)
(k) 1NT 3C Dbl
(l) 1H 1NT 2S Dbl
WHEN DOUBLE IS NOT TAKE-OUT 1. We have agreed a suit (not necessarily a fit). A suit response to a take-out double is taken as suit agreement. All the following doubles are penalty, or at least penalties in context, showing a balanced hand, such as (e): (a) 1S Pass 2S 3D (b) 1D 2C Dbl 3C (c) 1C* Dbl 2C 2S Dbl 3H 4C Dbl Dbl (d) 1S Dbl 2S 3H (e) 1D Dbl 1H 3C (f) 1C 2C* Dbl 2S 3S Pass Pass Dbl 3D Dbl 3C Pass Pass Dbl (c) 1C could be short, in five-card majors style. (f) 2C = Michaels, 5/5 in the majors. 2. We have pre-empted. The first two doubles are strictly for business. If you play a Multi, then doubles above 2S are also clearly penalty. Double of 2H/S over Multi (c) may soundly be played as take-out (best to agree; by the way, also agree what Redouble and Pass mean after Multi is doubled): (a) 2H* 3D Dbl (b) 1H 3S 4H Dbl (c) 2D* 2S Dbl (a) 2H = weak. (c) 2D = Multi, could be a weak two in either major. 3. A double of a naturally bid suit we have bid or implied is for penalties, as in (a) and (c). A short club does not count, so double in (b) is take-out. (a) 1S Pass 2D 2S (b) 1C* 2C Dbl (c) 1D Dbl 1H Dbl Dbl 4. When one partner has defined his shape (any rebid does this), then double is for penalties, for example: (a) 1C Pass 1H 1S (b) 1C 2C* 3C Dbl (c) 1C 1H 1S 1NT 2D Pass 2H 2S Pass 2D 2S Pass Dbl Pass Dbl (b) 2C = Michaels. 5. When they protect, except when an opening bid is passed by partner, double is penalty. Only the first three below are for take-out: (a) 1S Pass Pass 2D (b) 1NT Pass Pass 2H (c) 1NT Pass Pass 2C* Pass Pass Dbl Dbl Pass 2D* Pass 2H Pass Pass Dbl (d) 1NT Pass 2D* Pass (e) Pass Pass 1D Pass (f) 1S Pass 1NT Pass 2H Pass Pass 2S 1H Pass Pass Dbl Pass 2H Dbl Pass Pass Dbl Pass 2C Dbl (c) 2C = hearts/minor (Astro); 2D = non-forcing relay. (d) 2D is a transfer to hearts. 6. Double by a hand which had 'lurked' on the previous round is penalty, unless the opponents have shown a fit in time for his re-entry, and a take-out double is still conceivable. Double is penalties on (a) (b) and (d), and take-out on (c) and (e). (a) 1H 1S Pass Pass (b) 1S Pass 1NT Pass (c) 1S Pass 2S Pass 2D 2S Dbl 2S Dbl Pass Dbl (d) 1H 1S Pass 2S (e) 2H* Pass 3H* Pass Pass Pass Dbl Pass Dbl (e) 2H = weak; 3H = pre-emptive. 7. If they bid a new suit opposite a pre-empt, double is penalty, as below: (a) 3D Pass 4H Dbl (b) 1S 3D* Pass 3H (c) 2D* Pass 2S Dbl Dbl (b) 3D = weak. (c) 2D = weak. 8. When we double or redouble to express interest in taking a penalty (e.g. when they compete artificially or double for take-out), subsequent doubles are for penalty. All the following are penalty doubles: (a) 1H Dbl Rdbl 2D (b) 1NT 2C* Dbl 2H (c) 1NT Dbl 2C Dbl Dbl Dbl Pass Pass Rdbl Pass 2D Dbl (b) 2C could be any conventional defence to 1NT whatsoever. 9. If pass would be forcing, then double is business, as below: (a) 2C* Pass 2D* 3S (b) 2NT 3D Dbl (c) 1D Pass 2H 3C Dbl Dbl (a) 2C = Acol (game-forcing), 2D = negative. Some expert partnerships do not play rules 8 and 9, but it is much easier to play them, at the loss of little theoretical expediency. 10. (Optional) Support doubles by opener in fifth position. (a) and (b) show exactly three-card support, within almost any hand. (c) is simply for take-out. (a) 1D Pass 1H 1S (b) 1C Dbl 1S 2H (c) 1C Pass 1H 2S Dbl Dbl Dbl 11. (Optional) Action doubles by a hand not expected to act again, especially a pre-emptor, suggesting a better hand than already shown. (a) 3C 3H Pass Pass (b) 1D 2D* 3D Pass (c) 1NT Pass 2D* Pass Dbl Pass Dbl 2H 2S Pass Pass Dbl (b) 2D = Michaels. (c) 2D = Transfer. The double shows a maximum with three hearts. 12. Lead-directing doubles of various kinds. But a double of a splinter, or a double by a partner who won't conceivably be on lead expresses interest in competing in the suit: (a) 1H Pass 2S Pass (b) 1H Pass 1S Pass (c) 1NT Pass 3NT Dbl 3S Pass 4NT* Pass 1NT Pass 3NT Dbl 5H* Pass 6S Pass Pass Dbl (d) 2NT Pass 3C* Dbl (e) 1H Dbl Pass 1S (f) 1S Pass 3S Pass Pass 2H Dbl 4NT* Pass 5D* Dbl 6S Pass Pass Dbl (g) 1H Pass 4D* Dbl (h) 1H 1S 3S* Dbl (i) 1H 1S 2H Pass 3C* Dbl (a) 4NT/5H = Blackwood. Double says 'I have a void. Please lead it.' (b) Double asks for a spade lead, dummy's first bid suit. (c) Double says 'Please lead my running suit (i.e. lead your shortest)'. (d) 3C = Stayman (or Baron). Double indicates a club lead. (e) Double shows a top heart honour. (f) The second double negates the first, and asks for a non-diamond lead. (g) 4D = splinter. Double shows the playing strength for at least 3D. (h) 3S = splinter. Same again: enough to raise to three. (i) 3C = short-suit game-try. Doubler held: K J x x x x x x x A K Q x 13. Commonsense sometimes precludes double being take-out, even if it may be construed as such according to the rules. If in doubt, responder's trump holding should tell him what partner's double is, as in (b). (a) and (c) below are penalty. (a) Pass Pass 1S Pass (b) Pass 1C Pass 2C (c) 1NT* Pass Pass 3S 2S Dbl 3S Dbl 2S Dbl Pass 3C Dbl Dbl (c) 1NT = 15-17. 14. Doubles of no trump bids can also be take-out, chiefly of a no trump response to a suit bid. Best to explain by examples: (a) 1H Pass 1NT Dbl (b) 2H* Pass 2NT* Dbl (c) 1H Pass 1S Pass 1NT Dbl (d) 1H Pass 3NT* Dbl (e) 1D 1H Pass 1NT (f) 1S 3S* Pass 3NT Dbl Dbl (a) A sound take-out double of 1H. (b) 2H = weak; 2NT = enquiry. Double is take-out of hearts. (c) Double shows a penalty double of 1H (lurking). (d) 3NT = heart raise with a singleton spade. Double is take-out of hearts. (e) Take-out of hearts. (f) 3S asks for a spade stop. Double is penalty.