This quiz will describe a wonderful convention used by a big majority of the world's tournament players.
Suppose you have no special methods and RHO opens 2♠. You make a take-out double and partner responds 3♦. What will you do next?
Partner's 3♦ response has an awkwardly wide range, around 0-10. If you bid again with 16 HCPs, you may find him with a very poor hand. You may be doubled somewhere. If instead you pass with your 16 HCP, you may find him with 9 or 10. A good game has been missed.
A clever convention allows you to deal very much better with this situation, caused by the pre-emption of the 2♠ bid:
Lebensohl Responses to a double of a weak-two.
With 0-7 points, you bid 2NT
With 8-10 points, you bid 3♥, 3♦ or 3♣, your best suit
With 11 or more, you bid a game or maybe cue-bid 3♠.
We will see in the quiz how this works out.