Teams
Teams is a different format of bridge. It's actually the purest form of bridge, and most professionals play teams bridge, and the most prestigious events are teams.
In teams bridge you have a team of four players, two pairs. You play a match against another team of four players, playing the same boards and comparing results at just your two tables. (The rest of the room will also be playing the same boards but you don't compare against their results.)
One pair of the team sits North-South at one table, and the other pair sits East-West at the other table. An opposition pair will be holding the same cards as you and your pair, you are competing directly against their results.
Matches are usually 12 or 16 boards. It's possible to play shorter matches but the results become a little bit random, one board can have a large effect.
We take all the results from the two tables and compare each of them. It is the difference between the two scores that matters. So if our North-South pair scores 420 and the other North-South pair scores 420, there is no difference. If the other North-South pair scores 450 they have done better by 30 points, so there is a difference of -30 for our team, and +30 for their team. If the other team didn't bid the game and only scored 170, then the difference is 220, our team gain +220 and their team lose -220.
If we have made 420 and our teammates defeat the contract at the other table, gaining 100 points, then the difference is +520 to our team, -520 to the opposition team. (We have made a plus score at both tables, so these are added together.)
IMPs
These differences on each board are wide-ranging, it could be just one trick - 30 points - or the difference between a game and a slam, hundreds of points. One board might only gain or lose 50 points, another might gain or lose 500 points.
Because we still want the low-scoring boards to be relevant, there is a scaling system that reduces the scores to another range of scores. So each difference is converted in to IMPs, international match-points (don't ask).
This just scrunches the numbers down to a fairer scale. Now a difference of 1000 points is worth 14 IMPs, a difference of 300 points is worth 7 IMPs, so only twice as much rather than three times as much. It just stops the smaller non-Game scores from being swamped by Games or Slams.
So we play our match, say 12 boards, and the computer calculates the score difference on each board and then converts it to IMPs. A team will score IMPs on some boards, the other team will score IMPs on other boards, and sometimes the result is the same at both tables.
One team might score 1 IMP on board 1, 3 IMPs on board 4, 2 IMPs on board 5, 13 IMPs on board 7 etc
The other team might score 4 IMPs on board 2, 10 IMPs on board 3, 6 IMPs on board 6 etc
Team A Difference IMPs
Board 1 30 1
Board 2 -140
Board 3 -480
Board 4 100 3
Board 5 50 2
Board 6 -230
Board 7 780 13
Board 8 -100
Board 9 0 0
Board 10 200 5
Board 11 -50
Board 12 300 7
TOTAL 31
Team B Difference IMPs
Board 1 -30
Board 2 +140 4
Board 3 +480 10
Board 4 -100
Board 5 -50
Board 6 +230 6
Board 7 -780
Board 8 +100 3
Board 9 0 0
Board 10 -200
Board 11 50 2
Board 12 -300
TOTAL 25
So here we see all the results and the conversion to IMPs for each team. We then add up the IMPs for each team and this is the match result. Team A win the match by 31 IMPs to 25 IMPs.
VPs
In a knockout event Team A have won the match and proceed to the next round.
In a round-robin event, with say 6 teams, each team will play a match against each of the other teams, 5 matches in total, 60 boards, maybe over two or three days/nights.
Now, some sets of boards are full of games and slams, some not so much. An exciting match might have 80 IMPs at stake, and a team could win by 50 IMPs. The next set of boards might be quite unexciting, full of part-scores or failing contracts, and the overall score could be quite low, say 20 IMPs v 10 IMPs. And if you're the strongest team playing the weakest team, it would seem unfair that you can only gain 20 IMPs, but when your nearest rivals play the same team they could win by 50 IMPs.
So, we do a further scrunching calculation.
We try and make each match of similar value, regardless of the amount of IMPs at stake. Rather than the total IMPs, we look at the difference in IMPs between the two teams. So a score of 70 v 50 IMPs is worth the same as a score of 30 v 10 IMPs, the difference is 20 IMPs in both cases.
We convert the difference in IMPs to a new scale, called Victory Points (VPs). This scales each match down to a contest worth 20 points, the winners getting more VPs, the losers the opposite score out of 20. So the winners might get 16 VPs, the losers get 4 VPs. A drawn match produces 10 VPs for each Team.
So in the example above, 31 v 25, Team A won by 6 IMPs. Team A receive 12.01 VPs, Team B receive 7.99 VPs.
In a 6-team round-robin, each team playing 5 matches, the maximum score is five wins of 20 VPs, or 100 VPs.
Some Tactics
BIDDING
Bid games if they have a chance of making. Bid a non-vulnerable game with a 50% chance of making, a vulnerable game with a 35% chance. You won't make them all but you will make enough to be profitable in the long run.
The rewards for bidding and making slams are high, so don't be afraid to give it a go. Small slams are infrequent (about one every 15 hands), but they account for more than 50% of the swings at teams scoring.
Don’t bid a Grand slam unless you can count 13 tricks.
Aim for the safest contract. If you have a heart fit play in hearts rather than No-Trumps. 10 points extra doesn't matter in Teams. Be happy to play in a minor suit if that is safest.
Be careful when sacrificing. If you go down doubled in can be a big swing.
Take care dealing with pre-empts – bad breaks are likely.
Don't make risky overcalls, especially when vulnerable.
Vulnerable doubles and overcalls must be well up to strength. Partner must be able to trust them – more often than not he will have to take a view at an uncomfortably high level, with the stakes set high.
Don't compete too aggressively for part-scores. Often just Pass and let them play. Fight for the contract up to the three-level, then play for any plus score.
Don't be too bold sacrificing against game contracts. Let the opponents play their contract and hope you can beat it.
Don’t sacrifice against vulnerable games unless you are sure they are making. If opponents are playing accurately they will bid 40% games when vulnerable. So quite a proportion of even their freely bid games are going down anyway.
DECLARER PLAY
Just aim firstly to make your contract in the safest way. Overtricks don't matter much.
Take risks to make your contract if it looks impossible. Don't settle for quietly going one down rather than two or three (unless doubled).
Use safety plays to protect against bad breaks of the opponents' cards.
DEFENDER PLAY
Your aim is to defeat the contract ! Defend aggressively !
If you have the setting trick, take it. Extra tricks aren't so important.
Take a risk to set the contract, rather than trying to keep declarer to a minimum number of tricks. If declarer makes some extra tricks it doesn't affect the score as much as in pairs.
It's usually best to make your "normal" lead, don't go for glory.
Play steady, and avoid errors.