3♦ is a pre-empt 6 card suit is OK if you cannot bid 2♦ because you play Benji or you want to be more pre-emptive with favourable vulnerability.

South should pass as there is unlikely to be game.

West may overcall 2 or 3 ♠ in balancing position.

South then has to decide whether to bid. With no great fit and defensive values pass is probably right.

Difficult hand to bid.

Should East open 1 ♦ with 11 HCPs, but Qs and 6 card suit? Probably yes as safe rebid of 2♦ s.

West will probably bid 2♣ s to see what type of hand East has. 

2♦  shows weak and ♦ s. 

Choice now is to either explore slam or 3NT. 2♥  should be seen as forcing. 

East even though weak should bid 2NT as other suits covered.

South could bid 3NT as a duplicate result or 5♦ .

With 5♦ s and 5HCPs East can bid 1♦ .

After West jumps to 3♣ s the shape, points on the safe side of the strong hand and vulnerabilty suggests another double and South can bid 3♥ s with only 3 and the king as the best option.

North has a good weak jump 2♠ overcall.

South can pass or bid his ♥ s which is invitational.

West with a powerhouse will double again.

North passes as whilst good values does not have a ♥ fit.

With no defence  East should take out to 4♦ 

South should bid the lower of his two 4 card majors.

After Easts overcall of 2♣ s North can double to show the 4♠ s and South can bid 3♠ s 

1♠  or 4♠ s for East?

Perhaps a bit strong for 4♠ s, though it is a weak 13HCPs with Q doubleton and A singleton.

Either way West has enough values to either explore for slam via RKCB or just punt it.

West should bid the lower of 2 4 card suits (but the higher of 2 5 card suits).

North only has 10HCPs but a great shape for a double.

South should jump to show 8+ HCPs.

West cannot do anything and has to pass.

Open 1 or 2♥ ?

On points and shape perhaps 2♥  which will be raised to 3 or 4♥ s by East. South will then double and North finds 4♠ s.

Some will open 1♥ based on the fact it is a 7 loser hand with great 6/4 shape that one should bid more. Then should North do a simple overcall or a weak jump overcall. With a poor 10HCPs due to QJ doubleton and the pre-emptive effect better to bid 2♠ s.

Some may find the bid of 5♥ s as there are no defensive values in Wests hand.

3♦  pre-empt.

In principle East should pass, never pre-empt a pre-empt.

West has a difficult choice with 14HCPs, flat shape and only 3/3 in majors. If he finds a double then East will jump to 4s♠ .

With the vulnerability and knowing that E/W probably have game values South may find 5♦ .

North with 11HCPs and ♣ ,♦ or ♥ suits should pass the hand out as the opposition may find a mjor fit and outbid you.

There is a rule to guide you.

RULE of 15

The "book" rule on whether or not to open with a 1-level bid in 4th seat says to add your HCP to your number of spades. If the total is 15, open the bidding. If less than 15, pass it out. The theory is that it will be a partscore battle, and if your side doesn't have enough of the high-ranking suit, you could easily lose the battle.

So, you would pass out this hand:4K J 5 4K J 8 7K 9 8 7  (11 HCP + 1 spade=12)

but open: K Q 10 9 2A J 48 7 65 3 (10 HCP + 5 spades=15).

This rule is commonly called either "Pearson Points" or "Casino Count."

4♠ s will be easier to make, though in duplicate with 28+ HCPs some will go for NTs by West bidding 3NTs.

Slam is not the percentage option as it requires Q♠s to be finessed, but it drops which is not the correct way of playing 8 ever 9 never for the finesse. 

To open or not with 11 HCPs

With 5♦ s / 4♣ s an easy rebid to show  a weak hand and 5/4 so open 1♦  and then bid 2♣ s

With 5♣ s and 4♦ s more difficult so probably better to pass.

East cannot bid 2♥ s after 2♣ s as this would be fourth suit forcing and would get E/W too high. Just show a preference for ♦ s - the first bid suit and accept a 5/2 fit.

When you can bid again show your 5♣ s rather than 4♠ s. With a weaker hand Sojuth should show the ♠ s.

North reverses by bidding 2♠ s 16+ HCPs and showing at least 5/4 in ♥ /♠ s.

South can see 31+HCPs so should probably go straight to RKCB and bid the slam.

Should North bid 2 or 3♣ s? Bidding 3♣  makes it more difficult.

West can see East was probably 5♥ s / 4♠ s so a double fit, so should raise to game. 

Generally better to play in the 4/4 trump fit rather than 5/3 as you can use the long suit for discards.

North can pass 1♥ as with only 2♥ s in East / South hand someone will bid.

East needs to rescue the 1♥ doubled to 2♦ s.

North can probaby jump to 3NT as his hand looks stronger with the opposition points on his right.

Should West open?

11 HCPs but possible to rebid second suit so worth opening. 5431 is better than 5422. 

The rule of 20 says add your HCPs to the length of your two longest suits. So here you have 20, so open.

Open the lower of two 4 card suits.

Some may bid 3♥ s, but vulnerable it could be risky.

Over 3♥ s South has a difficult bid. 3N but low in HCPs. If South passes. North may double and then South bids 3N.

After East transfers to ♥ s West may bid 3♥ s to show 4♥ and a shape that supports game. With 9 trumps bidding to the 3 level is supported by the law of total tricks. http://www.bridgebum.com/law_of_total_tricks.php