The main question is whether to rebid 3S which may be passed by a weaker S, though in this hand they will raise 3♠ to 4♠. 

North may overcall 1♦ with a weak 2♥ jump overcall, then East can bid 2♠ being a free bid showing 8+ Hcps and 5+ ♠ s. Then west can raise to 4♠.

Some people may play Landy and West could bid 2♣ To show the majors.

East has an easy 2♠ overcall. As this is vulnerable it will be a serious bid and West can invite 3♠ and west can go to 4♠, though it is a difficult contract to make.

The question for East is whether to overcall or do a weak jump overcall. Though the hand has 11hcps 6 of these are from Qs including a Q doubleton that are not worth a full 2 points.

East can make things difficult by bidding 3Hs which should be seen as preemptive. With a strong hand and support using the unassuming cue bid would be better with 3♣.

4441 hands are always difficult to bid.

https://www.andrewrobson.co.uk/article/beginner_corner/1517

using this one would open 1♣ then west may bid 1nt to show 7-9 and a stop which East may pass. The shape is not great for 1nt so 2♣ is probably best then East may bid 2nt to show 15-16 Hcps and a ♦ stop, not a great one and risky. If east bids 2nt, west is better going 3♣ .

interesting flowcharts from Ebu.

http://www.ebu.co.uk/documents/education-and-teaching/pdfs/basic-Bidding-Charts-2008.pdf

is

The 2NT is unusual NT show at least 5/5 in the two lowest unbid suits. So here showing ♣ ♦ s. 

East will bid 4♠ s with this hand and some far weaker hands. Some people may bid 3♦ s (one of their suits) as an unassuming cue bid to show a good raise. 4♠ s being a distributional raise. With a choice of bidding ♣ or ♦ s one bids the higher suit to show values in the higher suit. This makes it easier for doubling a 5♣ ♦ bid.

When South bids 5♣ s West passes as minimumish and East has a difficult decision 5♠ or double.. Pass is not an option as E/W have game values. If N/S vlnerable double probably best even though ♠ s may only give 1 trick in defence. If E/W vulnerable 5♠ probably best.

For more information on unusual NT https://www.bridgewebs.com/dorking/page21.html

North 3♠ or 4♠ ?

North has 5 losers. West and North have 27 HCPs so south is likely to have 6-7 HCPs so may have the two winners needed for 4Ss KQ♦ or ♥ s or A♣ and a K. So 4♠ is probably best.

Then the question is what would be best lead for East? A ♠ or a ♥ which is a bit risky but with West with 1N has a high probability of A or Q and length as North did not try Stayman.

Whilst the contract shoould go down when ♣ s are played East must show count to show even number. With standard count he would play high 9♣ (5♣  may be ambiguous) showing 2 or 4. If he has only 2 then North will be able to enter dummy, so west must assume 4 and take the Ace straight away. 

Easier with reverse count as 2♣ shows 2 or 4.

For more information on count https://www.bridgewebs.com/dorking/page15.html

Straightforward until the last bid by East who has a 7 loser hand, 12 HCPs, no fit to partners suit and should pass though there are 6♦ s on due to the lay of the card. Some may invite with 4♦ s as 6 card suit and 6/4 distribution.

West's rebid 1Nt shows 15-16HCPs but the A♠ is not a great stopper. 3♣ would show shape and 16+HCPs, without a ♠ stop East would bid 3♠ as 4th suit forcing asking for a stop 3♦  would show less than 8HCPs) then West would bid 3NT and guaranteeing a ♠ lead.

2♦ Michaels showing 5/5 in top 2 unbid suits.

2♥ is good enough for West, East can always invite if a strong Michaels bid.

Another 2N unusual notrump showing 5/5 in lower 2 unbid suits.

South could bid 4♠s if this was taken as pre-emptive? 3♠ s would be game forcing.

West bids 5♣ s north will probably double and South will not like passing, but he should probably do so as K♦ s may be a trick and making 11 tricks is not easy. 

South could bid 2NT to show 17-18HCPs then easy 6NT by North.

After 3♣ by South showing 16+ and 6+♣ s. North knows 32+ HCPs and probably a good source of ♣ tricks so should probably bid 6NT 

South should open with great shape 5530 and rule of 19 (HCPs and lenght of two longest suits).

North has a good hand so show 5+♣ s.

East has an easy 4♥ bid.

South should show his shape with 5♦ 

West has great shape and North competes with 5♠ s

East doubles for penalties.

N/S have to play carefully to make 9 tricks (use the play button on the website to see how to play it correctly) for a top, but a bottom if only 8 tricks.

1NT is a great duplicate contract so South should show ♦ s if it is not conventional.

West should compete as well with his 5 card ♥ suit.