Things to remember
1) When you lead to partner’s suit : Lead high – low from a doubleton, low from 3 or more cards with honor, 2nd best from 3 or more cards without an honor (unless you agree for count leads, like 3/5) and top of sequence from a sequence of 2 or more. Based on this you can conclude that the ♣9 lead was from a doubleton (as the ♣10 is in dummy) and that is why you should not be hurry to play your 2nd top Club.
2) Overcall’s range needs agreement. My suggestion is to agree that 1 level overcall is 9-16 and 2 level overcall is 12-16. With more points – Double 1st and later bid your suit to show a big double (Super Overcall) hand (17-20 points). If you play a wider range for overcall (some play, say 7-18), then responder will have difficulty to bid his hand, mainly without a fit (what range would 1NT response be, taking in account that there could be game on, but also not wanting to get doubled by opponents if partner’s overcall is light).
3) Count is given by defenders when declarer initiates a suit (= on 2nd and 4th hand). Playing standard carding: High – Low will show an even amount of cards and Low – High shows ODD. Playing UDCA it’s the other way around: Low – high = even, High – low = odd. Playing REO: Odd cards = odd number of cards, Even card = even number of cards (playing high – low if odd number of only even cards, or if even number of only odd cards). Count helps defenders count declarer’s hand but also helps knowing when to win our top card (we usually want to win it on the LAST card of declarer’s short hand (so if we have AXX and dummy has KQJXX and partner played LOW to this tricks = he has ODD number = 3 cards = declarer has XX = we will hold up once and win the ace on the 2nd round)
4) A promotion can happen when a defender is laying over you and can’t follow the same suit: If you discard or ruff low – he will overruff with a relatively low card. If you ruff with a higher card – he will discard and his medium card (the ♥10 in the hand above) will get promoted. To avoid promotion you can do several things: Manage to pull out trumps fast before the above situation occurs (as with the hand above). You can also try to prevent the hand from the other opponent so that the suit which helps the promotion will not be played (you can’t do it here, but it could be relevant for other hands, for example, when playing loser on loser to cut communication). Another thing is to leave high trumps in both hands (if dummy doesn’t have the suit either).
5) Timing is everything. Sometimes it’s important to throw losers fast. But not with this hand. You could throw a Diamond loser on your 2nd top Club meaning there would be no rush to play a 2nd Club for a Spade discard. But sometimes you do need to rush. Example:
You play 4♥ and N leads the ♠Q. You have 4 losers, 1 on each suit. If you play a trump at trick 2, opponents will win and play a 2nd Spade, and now you will lose a Spade trick along with 3 aces. So, realizing you can’t afford to lose a Spade, you need to develop Diamonds fast to allow you to discard your Spade loser on the last Diamond (make sure to win trick 1 in hand and keep the ♠A as an entry to the 3rd Diamond).