Don't trump your partner, unless you can cover the trick and remember if your partner trumps your honor lead, keep track and count it as one of your tricks. (unless you have no clue how your partner plays or are pretty sure he has no clue how he plays either)
If your partner leads boss or plays boss and you are void in the suit don't trump it unless:
You believe the person who follows you is void in the suit and in this case you better trump high.
You are trying to avoid taking a bag.
In general never cut a 13th card lead from the second seat. Your partner will always have the last play and cut accordingly.
Bid correctly for the situation. For instance: If the score is such that you will lose the game if you do not set them, and you are the last person to bid, then push the bid to a total of 14. It doesn't matter if you can't make it, because you'll lose either way. Your partner may have underbid.
Bid your Kings but be careful. Most Kings fall because of improper leads and play. The King is trumped almost always on the 3rd time the suit is led.
If the person on your right leads, even with the queen, you don't have to play your king. Odds are the person on your left will play the Ace if they have it or let the Queen go.
If the person on your right leads a suit for the first time and you are holding the queen. Evaluate your hand. Is it evenly distributed? Will the suit likely go around 3 times? If the suit is likely to only go around twice play the queen. This forces the person who plays after you to play the king if they have it, if they don't have it and the person who led has it, you just picked up an extra trick. Unless of coarse they are holding the Ace.
If your partner leads a spade, evaluate what your partner bid. Did your partner bid spades? Is your partner trying to set or not to bag. If your partner is possibly trying to set and leads a low spade, play your highest spade and lead back spades if you take the trick. If your partner is trying not to bag, they may lead a high spade to give you a chance to dump a high spade or to dump their high spade.
When avoiding bags, lead your short suits first to attempt to get rid of a suit ASAP. If that suit is led, and you have discarded it, you can then slough or trump your partner as necessary.
Covering a Nil:
If your partner has a nil bid, always cover the nil first. Don't let your partner get set because you are worried about bags or getting set.
Don't leading a suit that one or both of your opponents are a void in and your partner has. This can be one of the worst leads possible, especially if one of your opponents is nil and void in the suit. What occurs with this lead is it allows your opponents to dump high cards and spades that may be required to cover your partner's nil. Example:
If there arenít more then three bags and you have a weak cover hand, take the bags as soon as you can. This will force the other team to concentrate on making their bid. If your partner's nil gets set, then your opponents bid gets set.
If your partner is going nil try to confuse your opponents. If you have a high streak in a suit play, don't play the highest card you have in that suit first. Your opponents may believe your partner has the higher one(s). Example: You are holding the Ace, King, Queen Jack in a suit. If you play the King then the Queen your opponents may believe your partner has the Ace.
If your partner is going nil, you know your partner is void in a suit AND you play before your partner, trump with a high spade. This allows your partner to dump a high spade and your opponents will still have their high spades to cover with too. If you don't have a good suit to comeback in or you are going to have to cover a different suit with spades or you really need to throw off a different suit you might not want to do this. Keep this rule in mind if your partner maybe trying a 4-spade nil.