In bridge, thinking about position is imperative. You must figure out when your honors are well placed and when they are badly placed—first with the bidding and then more fully when Dummy is revealed. As defenders, you must stay aware of times when the two of you have to attack different suits from opposite sides of the table due to positional issues. Here are two example hands from San Diego Bridge Club today, August 7, 2018.
Hand #19 Partner passed; RHO passed and you passed with ♠54 ♥J654 ♦J5 ♣AJ1032. LHO opened 1♦ and your partner overcalled 1♠. RHO made a negative double; you passed and LHO bid 1NT ending the auction. Partner led the ♣9 and Dummy produced: ♠76 ♥A982 ♦K72 ♣Q874. Declarer called for a low card from Dummy. Clearly partner has led “top of nothing,” hoping to find your suit/your entry. She has found both. The question is: should you hop up with the Ace now (giving Declarer TWO club tricks) in order to lead a spade for your partner from your side of the table? Looking at Dummy should clarify your decision. Partner should have ONLY five spades—she had a chance to open a Weak Two bid and passed, and she had a chance to bid 2♠ over 1♦ and bid only 1♠. That means Declarer should have four spades. So, one lead through from your side will NOT be enough to wrap up the suit for partner. Wait until next time around. Play your ♣3 (as encouraging as you can get). When partner wins a trick, she'll return another club and you can take three club tricks. Then you can lead a spade through for partner. If you hop up with the Ace, you'll give Declarer an overtrick he does not deserve. (Partner's hand was ♠KJ832 ♥Q1073 ♦A9 ♣95. Declarer bid NT with singleton the ♥K and ♠AQ109 ♦Q108643 ♣K6.)
Hand #17, same place, same date. You held ♠96 ♥AKQ ♦KQ106 ♣10532 and opened the bidding 1♦. LHO passed; partner passed and RHO doubled. [This was the incorrect bid, but you did not know it at the time.] You pass and LHO bids 1♥. Partner passes. RHO bids 1NT (ostensibly showing 15-18 HCP) and LHO raises to 3NT. Your partner has 0-5 HCP and, if the opponents have their bids, more like 0-2 HCP. Your whole objective should be to NOT finesse yourself. Position tells you that the diamond strength is expected to be on you right, so don't give Declarer a “free finesse”—and a trick she could never get if you hadn't led the suit. Don't worry about finessing partner. So, you cannot lead a diamond. You could lead “top of nothing” in spades, or a fourth best club (perhaps partner will have the Jack), or the ♥Q to look at Dummy. If you lead a fourth-best diamond, Declarer will make the hand. If you lead any suit other than diamonds, Declarer will be down one. Dummy: ♠J853 ♥7653 ♦A95 ♣A8. Declarer had: ♠AQ107 ♥J8 ♦J873 ♣KQ7 and misbid. After 1♦ by you/pass/pass the next hand SHOULD have bid 1 (balancing) NT showing 10-14 and a diamond stopper. It was incorrect to double with two cards in an unbid major [her ♥J8]. When her partner bid 1♥, she ran to 1NT in fright and her partner, expecting 15-18 (doubling and THEN bidding NT in the balancing seat promises that range), raised her to 3NT. Declarer always has four spade tricks (with finesse working); three top clubs and one top diamond. However, no ninth trick is available, as long as the defenders break diamonds.