When a partner makes an unusual bid ...

One of Karen Walker's bridge themes is to advise "Think about partner's potential problems". In other words, what do partner's bids mean? Especially when faced with an unusual bid, pause a moment to think about what could have prompted partner to bid that way. Playing online, we made bad decisions on two deals that illustrate her point.

Partner bids spades, and when you raise to 2S, he bids 3NT. What do you do?

Don't just bid 4S because you have four spades. Your earlier 2S bid already showed that you had four spades. The normal thing for partner to do would be to bid 4S. He didn't, so what is he saying? He's saying that he has a balanced hand and his points are all outside of spades i.e. he feels that 3NT is the place to play unless you have a distributional hand.  Do you have a distributional hand? A 5-4-2-2 hand would be distributional, but a 4-4-3-2 hand is practically balanced. And even in your doubleton suit, you have a Jack. Pass the 3NT.  4S goes down 1.  3NT makes.

A few hands later, you bid 1S, partner bids 2C (you play 2/1, so this is forcing to game). You bid 2NT and partner raises to 5C. What do you bid?

Again, what is partner saying? He is saying that he wants to play clubs. What clubs have you promised him? Probably two, maybe even 1. So, he probably has a self-sufficient 7-card or longer suit. He must have outside entries (since he bid 2C). So why did he make this 5C bid? In this auction, if he bids 3C, you would just bid 3NT with a diamond king (and maybe pass without a diamond stopper). Either he doesn't want to play 3NT or he doesn't want to stop short of game. The bidding problem for partner is that he has clubs and no diamond controls. 4C would be Gerber and he can't do that with doubleton diamonds. If you stop to think about it, your action should be obvious.

Your two aces are golden. One is in partner's suit and the other will win the first trick. Bid 6C.  On this hand, 7C and 6NT easily make.  In clubs, you can establish the spades and throw your diamond loser on the good spade. Dummy's clubs give you two entries even if they lead a diamond on the get go.  7NT also makes because East gets squeezed between hearts and diamonds, but I don't know if I will be alert enough to follow East's diamond discards. to know that my 8 is good.