I have 15 to 17 HCP and a balanced hand → Bid 1NT.
I have 20 to 21 HCP and a balanced hand → Bid 2NT.
I have 13 to 21 total points → Bid one of a suit.
I am in first, second, or third seat, I have 5 to 9 total points and:
- A 6-card suit other than clubs → Bid two of the suit.
- A 7-card suit → Bid three of the suit.
- A 8-card suit or longer → Bid four of the suit.
I have 22+ total points → Bid 2♣.
None of the above apply → pass.
One-level suit opening
- I have a 5-card or longer major → Bid 1 of that major.
- If you have at least 5 cards in both majors, bid the longest one first. If they are equally long, bid spades first.
- I have three clubs and three diamonds → Bid 1♣.
- I have more clubs than diamonds → Bid 1♣.
- Otherwise → Bid 1♦.
Notes on one-level openings
Many players use the Rule of 20. in first and second seat. According to this rule, you can open at the one level if your HCP plus the lengths of your two longest suits is at least 20, otherwise you should pass.
In third seat, if you do not have a Rule of 20 opener, some players would open anyway with 10+ points and a good five-card suit or longer. The idea behind opening "light" in third seat is to preempt the left-hand opponent from opening.
In fourth seat, some players use the Rule of 15. According to this rule, you should open at the one level if your HCP plus the number of spades you hold is at least 15, otherwise pass. The idea behind this rule is that if you pass, both sides score 0 points, whereas if you open, there is a risk that the opponents wind up with the contract and win points. The more spades you have, the more likely it is that your side will have the contract, since spades is the highest suit.
Notes on weak openings
The purpose of a weak opening is to preempt the opponents, depriving them of bidding space. For example, if you are in third seat and you open 2♠, and your left-hand opponent was considering opening 1NT (showing 15 to 17 HCP and a balanced hand) then they can no longer do so and will be forced to pass. If your right-hand opponent has 10+ points, the opponents will have a game but not be able to bid it because you have disrupted their ability to communicate. Go you!
If you are in fourth seat, there is nobody left to preempt. Therefore, preemptive openings are not used in fourth seat. You have a weak hand and your partner has an average to weak hand, therefore it is better to just pass and move on to the next board.
Preempts are most effective in the third seat since you already know that your partner does not have a strong hand, so the opponents almost surely have more strength than your side, and your preempt can prevent them from finding a lucrative contract, while not hurting your side in the same way. If you preempt in first or second seat, you take the risk of depriving your partner of bidding space, which is bad for your side. For this reason, some players will decline to make a preemptive opening in first or second seat if they have a good 6+ card major suit.
The risk of a preemptive opening is that your side won't be able to make the contract and the opponents will score undertrick points. For this reason, some players only make preemptive openings with good suits. The more unfavourable the vulnerability, the better the suit needs to be.
2♣ is not a preemptive opening because it is reserved for strong hands. If you have a 6-card club suit and a weak hand then you cannot express it by opening 2♣. With a good quality 6-card club suit (such as KQJxxx) you can consider opening 3♣ instead. Otherwise, pass.
Some players use 2 and 3 level opening bids in fourth seat. Again, these are not preemptive. Instead, they show a good-quality 6+ or 7+ card suit, respectively, with slightly less than opening strength (typically 10 to 12 total points). We do not cover these bids in this flowchart.