At the "Main Menu", press "Shift + Alt + A" to enable cheat mode. During gameplay, press any of the following:
Alt + K -> Free building, no resources required.
Alt + C -> All missions.
Alt + X -> 100 gold plus 100 popularity.
Alt + B -> Extra soldiers
Bonus peasants
You can get lots of extra peasants (more than the limit of 24) by doing the following. Put your Quarries and Oxen to sleep. Now there will be that many more available when buying Swordsman etc. Just wake them up when you are done. This is useful if you don't want to wait until for your Peasants to fill up the campfire, or you just need them right away.
Find enemy killing pits
Select an engineer and press the build button. Then press on something to build but don't place it anywhere. Just move it around the floor and occasionally it will go red though there is nothing to stop it. There will be a red square some on the floor of where you want to place the tent and that will show you where the killing pits are.
Battle tips!
Ok if you are loaded with Gold and can use alot then you should make a army of one unit. Like horse arches witch can be very deadly since they can move and shoot and avoid most attacks. And should consider making arab arches instead of reguler arches because they are faster and do about the same damage.
No resources tip
If you can't get food and wood and resources, you should keep the population down to make food last longer and make taxes and buy food and stuff at markets.