Here is a simple guide to the fundamentals of Castle Siege that you need to know if not already, and some useful information that you can use. You can find further and more exhaustive information Here.

Registration
All alliance members can submit Signs of Lord to the Guardsmen NPC in Loren Valley during the registration time. The three alliances with the top registration ranking will be those that partake in the event. Anyone can participate in CS regardless of guild or alliance, but only alliances stated in the announcement can win the event. Others involved will appear as neutrals.

Siege Warfare
Neutrals can kill only with Ctrl, and they will obtain outlaw status. In the Siege warfare however the attacking, defending, or neutral alliances cannot drop items in dying.

The Castle
There are many components encountered throughout Loren Valley and the Castle. These include Siege weapons, Castle Gates, Guardian Statues, Guard Towers, Dragon Tower, Castle Seal, and Life Stones.
Siege weapons
They are positioned at the fields of the invading and defending teams. You can select and view the location being attacked while using them.
Castle Gates
These Gates have HP that need to be attacked during the Siege, and destroyed. Take care of your weapons while attacking them as they will greatly reduce durability. Castle Gates cannot be repaired during the warfare by the defending alliance.
Guardian Statues
When the four Guardian Statues inside the Castle have been destroyed, the blocked entrance into Dragon Tower will open. Only the defending alliance can enter. Again weapon durability is greatly reduced when attacking the Guardian statues.
Guard Towers
The Guard Towers protect the Guardian statues, and attack the invading alliance. These towers can be attacked and destroyed. once the battle starts.
Dragon Tower
This tower is located at the top of the castle. The top floor of the Dragon Tower is where the Castle Seal is for the Castle Lord.
Castle Seal
When a Guild Master of the alliance registers the Castle Seal in Dragon Tower, they will now have to defend the Castle.
Life Stones
There is a 60 second timer in positioning the Life Stone. They can only be used by the invading alliances, and can be destroyed by both invading and defending guilds. An attacking guild member will respawn at their alliance Life Stone after being killed. It also has HP, Mana, and AG healing abilities.

Castle Lord
Only the Guild Master can register the seal, however the battle continues until the Siege warfare time is over. The guild with the Castle Seal registered at the end are the Castle lords.

Features
Warp command will not work during Siege warfare. Defending teams can however use Town Portal Scrolls to appear at the Castle entrance.
Tab to remove the Mini Map at the lower right of the screen. All members should know their location and role of their party.
Potions are required for destroying the castle gates and statues. Your weapon durability will deteriorate when attacking Castle gates and Guardian Statues without first taking the potion. You can make these items prior CS using the Chaos Machine.
Potion of Bless lasts for the 60 seconds. It will increase damage to Castle gates by 20%. However it does not apply to damage in PvP combat.
Potion of Soul lasts for 30 minutes. It will increase attack speed by 20, and increase defense against Lightning and Ice attacks by 50%.

Announcement and Preparation
During this time the top three chosen guilds will be announced for the Siege. They will now have the chance to prepare by buying potions, creating Life Stones and do some planning.

Castle Siege Begins
The objective for Castle Siege is to destroy the four Guardian Statues, enter the Dragon Tower and then stamp the castle Seal. Then the winning guild must then successfully protect the Castle until the Siege is over.

The attacking players start outside of the castle walls. They must destroy at least one of the three Gates in order to enter the outer perimeter. Once one of the Castle Gates has been breached there will be two Guardian Statue and two Castle Gates. The Guardian Statues must be destroyed and one of the Gates must be breached.

Passing the second set of Castle Gates, there will be another Guardian Statue and yet another Gate. Both Gate and Statue must also be destroyed.

After breaching the second Gate you will have to destroy the last Guardian Statue to gain access to the Dragon Tower. If some of the Guardian Statues are still standing the force field surrounding the entrance to the Dragon Tower will not disappear. The only way to remove the Force Field is to destroy all Guardian Statues.

Once inside the Dragon Tower, there will be a room. Inside the room are two switches and a pedestal. Two members from the attacking alliance must activate both switches at the same time for around 20 seconds. Then the Guild Master of the attacking guild must click on to the pedestal to stamp the Castle Seal. This process takes around thirty to forty seconds.

If this process is not completed properly a force field will appear over the pedestal for a few minutes. Then the process must be repeated.

If the Seal stamped successfully then the winning alliance will take ownership of the Castle and all the other guilds will be removed from the Castle. The winning alliance must now try to defend the Castle for the remainder of the event.

The last alliance holding the Castle at the end of the Siege will win.