Are your messages clear to your partner? Does partner have a clear idea about the shape of your hand? It’s easy to make a mistake and mislead partner.
Partner has opened 1♦. What is your response?
When you are choosing which suit to bid, try and anticipate your next action. The future path of the auction is sometimes fairly predictable. If you have no idea how the auction will go, think about what your next bid will be if partner forces you to bid again.
Mistake: Bidding the lower of two 5-card suits
It is a good idea to bid your suits up the line when you have 4-card suits. You hope to find a fit along the way, but, if you have two 5-card suits, you need to show those suits to your partner in such a way that it is easy for partner to choose at the correct level.
If you bid 1♥ first, then you have to bid 4♠ over partner’s forcing 2NT. Partner prefers hearts so will have to bid 5♥ which will go down. Bidding the spades first allows partner to choose hearts at the 4-level.
Players frequently offer each other a choice of two suits. It doesn’t matter whether you are opener or responder. The principle is the same for both. Bid the higher-ranking 5-card suit first and keep the auction low with 4-card suits.
Principle: Bid the higher-ranking 5-card suit first, both as opener and as responder.