You can get a huge amount of stone and wood by
following the following steps:
1. Build a castle with 1 ton stone and 1 ton wood
(or as less as possible)
2. When the castle is built, extend the castle design
to use 100 tons of stone & 100 tons of wood
3. As soon as you exit the castle design screen, demolish
the castle. You now have over 65000 tons of stone and
wood!!

To surrender a big castle
-------------------------
Let 1500 archers shoot at the archers in the castle. When
they are put to death, press autocalc battle. The castle
is yours.

400 farmers, 400 knights, 200 maceman
-------------------------------------
First, let the farmers slam shut the canal. Destroy the bridge.
Destroy all cans with a knight, and defeat the other soldiers
with your knights. Destroy the middle gate with your maceman,
defeat the rest and take the flag.

To defend a castle
------------------
Put as many archers and crossbow-men into battle as you can and
let the computer decide. If you don't have these men, then
defend with knights and pike-men.
 

HexCheat
--------
Load the savegame into the hexeditor and change the offsets
87.990, 87.991 and 87.992 to FF. Now you should have enough
money.