Warning: It's been a while since I've played this game.
Here's some decent tips:
How do you defend properly?
There are few things as annoying as being raided, and here are some tips:
1: Use natural chokepoints!
You can build those scout towers, and you can use guard mode too, to set watches.
If you have chokepoints, such as river crossings and mountain passes, put a defensive stack there. This way you might be able to use 2 stacks to defend against just about anything, and not need full stacks in every city.
2: Defensive stacks are different from offensive ones. They have different needs, and different strengths. A good *basic* defensive Human stack is:
4x Pikemen
4x Ballista
The formation is like this:
[ENEMY FORCE]
P P P P
B B B B
This way, they'll weather a storm of bolt-fire, and their cavalry have to face pikes, which they won't like. This is not a be all, end all stack, but it's a good starting point.
The idea behind a defensive stack is to HOLD the enemy, and shatter them. If they have the ranged advantage, they will force the enemy to move within range quickly, and they will force the enemy to spend their movement points moving towards you, instead of around you. This way you won't need much speed. If you defend a settlement, you have an additional advantage in that you don't have to worry about breaching the gates. And Ballistae are good against rams, the cheap level 1 siege unit.
ALWAYS have a stack in your city. It doesn't have to be a big stack, but you don't want that single flyer to take out every city you own. 2 archer type units is enough for most of the low-tier flyers. I'm not saying a full stack, just a small one.
When fighting defensively, realize that you have a very simple objective: Smash the enemy siege weapons and flyers, and hold any breach.
That's it. You want heavy infantry and ballistae to do this, as ballistae are cost effective bastards, and heavy infantry will slaughter their lighter brethren. (Orcs are surprisingly good on the defensive if you play them this way. Swordsmen and Warlords are very good units, and their ballistae are cursed for that extra oomph. Dwarven Cannons make for the good-guys' defensive specialists.
Raiding in force:
This is when you have a stack of mobile decent troops, that can go far, and kill smaller stacks without much worry. Halfling riders, Azrec elephants, human medium cavalry, etc. are good examples. (Halfling riders are the poorest ones statwise, but a size 2 city can crank them out every round! You can swarm the enemy with cavalry this way).
Raiding in force is a good way to take care of artillery heavy stacks, as you have the mobility to get into melee before they shoot you to pieces. If the enemy employs pikemen, take down the artillery and run away. Let some other stack take care of the rest. :)
Siege: Remember that you have plenty of time.
Don't rush it. Remember to choose units that fit the purpose. You want cavalry and heavy infantry to rush into any breach, artillery to make those breaches happen, and maybe som flyers if you have them, or something similar to go get those pesky ballistae.
As for strategic advice: Raiding in force is expensive, you can get 4 stacks of 2 cavalry instead and spread out much more quickly. However, it gives you the flexibility to overrun early settlements. Azrecs and Halflings should aggressively pursue this strategy, since they have good level one raiders. (Elephants can knock down walls!) Everyone else might want to wait it out. If your opponent fortifies it might seem like a waste, and even capturing smaller settlements seems like a waste when you know he'll retake them pretty soon.
Thus, my advice is: Send those stacks in deep. If you can afford a stack of 8 cavalry not being a part of your main forces, it's likely rather late game. Send them deep into enemy territory, and have them raze EVERYTHING they can get their hands on. Remember that units cost money, and everything you deny him, he can't use against you. Raze nodes, mines, waterwheels, construction yards... Everything.
This strategy is most effective with azrecs (elephants!) and halflings (Pony Riders!), but can be used by any race.
Andy_Panthro: OK, here's what tends to happen with the first mission of the Cult of Storms campaign.
One of the issues I have is that you're constantly on negative gold per turn.
This is because you start the game with several units and no towns/mines.
You only begin with 250 gold as well.
Even when I get three towns (goblin, two elvish) and two mines I still barely get into positive gold per turn (when they are producing merchandise).
And because that takes a few turns, my 250 starting gold is almost all gone (and it takes 80-90 gold to take the goblin town without a fight).
This means I can't really make any units or fortify those towns, and with no new units I can't expand any further.
Then the mines get stolen from me because I don't have the units to protect them.
Listen, all you have to do is to kill the keeper leader. (Your boss' mother.)
Just pack all your strongest units together, and head north. Let the other crap run free. :)
Your stack should be 4x wolf raiders, 2x Orc assasins, the big beetle and yourself.
Just run like hell to the north, and assault the walls. Everything else is optional, although conquering the cities in the middle of the map gives the elves something to do in the meantime. That's how I did it, in about 5 minutes.