Tuto Defence
I'm often asked how to defend my castle properly. The defence starts with: having a good castle, then comes the placement of troops and finally the cards. The castle, I invite you to look at the tutorial on building a castle.

A player who pops, looks for 2 things: Gold on your provosts and castles that are easy to capture, to get weapons and troops. So, the easier you are to capture, the more you will be a target.

Here are two videos where you can see the difference between a good castle and a bad one (badly defended).

Une capture facile
À ne pas Faire

Château non carté,
Plusieurs attaques pour la capture

Cliquer sur les autres attaques pour voire la
suite : Château non carté

The troops,
It is important that you place a minimum of 400 troops on your village. The suzerains also play an important role, as this will give you more freedom to make merchants and monks. Moreover if you have a good suzerain it will allow you to play the card of : Improved Guards houses, it costs 10 map points and will allow you to place 520 troops on your castle. Without a suzerain you will be limited to 500 since this is the maximum number of troops you can recruit in your village. Otherwise you can also send reinforcements from a provost or one of your villages, but they will no longer be available for the latter.
Carte 520             Carte 560

Cost in cards points 10 and 200
If there are good and bad suzerains, it is the same for vassals, it is important to place your suzerain's troops behind your troops
Here we are, we have 520 troops, on the villages, we have placed the troops of the suzerain, behind ours, now the pikemen, some of them are aggressive, others are defensive, it is important to have a maximum of pikemen (about 150 in my case) because if you have a lot of archers, but no pikemen, there is nothing that will prevent the enemy troops from advancing.

Aggressive Prikemen
you see the sword in red next to the pricker
indicating that the Prikemen is aggressive.

Defensive pikeman
you can see the green shield next to the pikemen indicating
that they are defensive. (pikeman at the exit and in the dungeon)

There are several playable cards in defense, some more effective than others, you say which card to play or not it's rather difficult depending on the type of attack, their number and so on... so use your judgment or get out $$$$ ;-)
Double the rate of fire in the Dungeon
The difference is the duration - 2h - 12h or 1 day.
Improved pits
you can buy the 1.5 - x2. The x4 you get it
I'll put them on if I don't...
I like these cards, the opposing troops burn very well ;-) here you can buy the 1,3 and 1,6 but if you have the x2 ouff it makes a nice BBQ.
Improved stone Structures

I always use the 1.8 you can buy the 1.5 & 1.8. The x2 you receive it
Improved moat
I use the 1.5

you can buy the 1.3 - 1.5. The x2 you get it
Improved stone walls

I use if I have
you can buy the 1.5 & x2. The 2,5 you get it

Card good to sell, useless, if you have a wooden castle... I invite you to go back to see the tutorial on Castles. There are some who say that it improves the resistance of the balistes, but as it is not indicated... it remains to be seen...
These are good cards, it always has the cost in card points, but, high beyond their cost, you have to consider your castle if you play a superior ballista and you have 2 ballista in the castle it will not be very profitable. Same thing for the Turrets, for the Tunnellers make sure you have a peasants' hole in your castle and that the Tunnellers' Guild is at the best possible level. If it's level 1, I think you can switch to another map.
On one side, the desperate defense, it once launches the order, to repair the castle - if you are attacked.
On the other side, the last stand, they bring out a group of knights towards the end of the siege (when the enemy troops arrive near the dungeon). These cards are super useful, plus you can play them repeatedly during a sync.
Charge of Knights
x2 knight's speed
There are some people who say that it makes the armed peasants go faster, but that remains to be confirmed
Surprise Attaque
Group of Knights makes an exit at the beginning of the siege. Either 2, 5 or 12 Knights come out of the dungeon in addition to your Knights.
It is important to watch the menu at the top right, if you see the 2 crossed swords that flash this indicates, if you receive attacks (AI, Players) and scouts if you click disappointed you will access several important tabs and will be able to see the attacks and their time.
The little green circle that you see in the corner, on the world map seems insignificant, but, it's really very important, because, it's the refresh time (35 sec) it's already long, but if you deselect the game, like me writing here, my refresh is longer. So in 30 seconds, I can put what 3 armies in sync at 1 minute, it can hurt.

The scouts tab

tells you the time and where the Scouts come from. If a player scouts you, the swords will start flashing. No need for a village ID for a scout.

The Monks tab

tells you the time and where they come from. If a player sends you monks, the swords won't flash. ID your village and we'll warn you.  
The Attacks tab

tells you the time, where the Attacks come from and the type of attack. If you see as above captains. it's time to draw the cards ;-)  The swords will blink of course.
Small Scenario

You log in and see the swords flashing, don't panic it's only villages, once the breaths are taken, you can see which village is attacked, have the forbidden (to prevent other armies from being launched) or have played dead (to try to crash as many armies as possible) It could also be exco. So, after have judged the solution to be taken ... Here are two examples:

You just have an opening army and the captain - your castle is well closed with 520 troops - it's defensible. Play a few defense cards, forbid it or play dead.

You have 7 armies and 5 captains - This is hotter - first thing to do exotic your village (if it's possible before the enemy armies arrive if your monk arrives after it's not worth it) you can play your favorite defense cards, make donations to the provostry (weapons, beef and resources) break the ID (banning the village just before the troops arrive, or even with a teammate to sync a counter raid capie or recapture, just behind the enemy armies. Why not just raze the village before the enemy armies just to make it lose as many troops as possible
For me, having a TS3 is important...
The use of a TS (TeamSpeak3) is very useful to get advice and organize yourself well, write and play when you concentrate on defending or attacking not very obvious, especially when you have to explain everything, then, on TS you just have to communicate it vocally, you send a message: Urgent attack come on TS and the players present on the game come back on TS. That way another player can send the information by message and we can better coordinate. (better reactivity)