Tips spades

Beware the bags, but it's almost always better to underbid than to overbid.

If you have a lot of spades, bid higher.

TIPS FOR GOING NIL -

If you have a short suit (1 or 2) that is good. Hopefully they will be played AND you can throw away a card on the 3rd run of that suit.

If you have face cards but also 3 smaller cards in a suit, that is good because you can play the 3 small of the suit (AND probably almost 12 cards will be gone of that suit then). But if you have K or A and only 2 small in the suit - the 3rd round might be yours UNLESS luckily your partner only has/had 2 and now is free to trump.

Can your partner beat a high card?

If you have the queen of one suit, there is a 55.5% chance that your partner has a card to beat it (i.e. king or an ace). So even if your hand with a queen of spades is otherwise very weak, you should not go for a nil unless you are behind by many points, as the base success rate is only 55% [you can only expect 100*0.55+(-100)*0.45=10 points from the play, and will likely saddle your partner with bags].

If you have the jack of one suit, there is a 70.3% chance that your partner has a card to beat it.

If you have the ten of one suit, there is a 80.2% chance that your partner has a card to beat it.

Who is undersuited, and by how much?

If you have two cards of one suit, there is a 3.3% chance that someone has no cards of that suit (1.1% chance that your partner has no cards in the suit, and 2.2% chance that either of your opponents has no cards in the suit); 19.2% chance that someone has only one card of the suit (6.4%, 12.8%); and 47.7% chance that someone only has two cards of the suit (16.9%, 33.8%)

If you have three cards of one suit, there is a 5.1% chance that someone has no cards of that suit (1.7% chance that your partner has no cards in the suit, and 3.4% that either of your opponents has no cards in that suit); a 25.8% chance that someone has only one card of that suit (8.6%, 17.2%); and 58.5% chance that someone only has two cards of that suit (19.5%, 39%).

If you have four cards of one suit, there is a 7.8% chance that someone has no cards of that suit (2.6% chance that your partner has no cards in the suit, and 5.2% that either of your opponents has no cards in that suit); a 35% chance that someone only has one card of that suit (11.7%, 23.4%); and 70% chance that someone only has two cards of that suit (23.3%, 46.6%).