What difficulties you having?
I, personally found hiring a commander, exploring for a couple of turns around your stronghold until getting 2 swordsmen and 2 bowmen, than looting some crypts, than going conquering the easiest way to go. Develop ranged tactics as much as you can, and have more shooters than melee units. Once you can, get horse archers. Make your commander a Tactician at level 10, so he'll pimp your shooters even more, and will be a badass himself. Bowmen I believe to be much better than crossbowman because he's much more mobile and has got longer range, meaning much more tactical opportunities (also, it will range dwarven siege engines quicker). Swordsman or Pikeman may both work, I was rocking with swordsman. If you want Pikemen, make sure to weaken your enemies with arrows, do not kill them.
Why?
Campaign-wise your units will be much less damaged, which enables longer maneuvers without halting to heal. Battle wise you will be pawning your enemies. If you took ranged tactics, leveled your bowmen a few times you should easily have about 7-8+ ranged attack with them, that's plenty to hurt units that you would normally consider ranger-proof, such as the dwarf or the swordsman. On my last shard I was shooting 10-11s into swordsmen, while with ranged attack 5 you can barely scratch them. End-game (on the shard you're at) you will have 10+ shooters, each shooting with a force of 8-9+, what not to love? I haven't progressed that far to the game, but I wager if you got lvl 5 ranged tactics you would REALLY dominate.
Other useful skills are defensive tactics for ranged defense (it's a nuisance to get your shooters shot down), discipline for resistance and extra hp, maneuvering for extra stamina.
Tips for battles:
Keep your distance. You can play around and drag your enemies if you count their and your available moves. Delaying the melee with 1-2 turns can mean the difference.
Strike first. If an enemy has got 1-3 hps left, move in with your swordsmen or commander and finish it off, saving an extra shot for something that's still uninjured. You will also spare your precious hp from counterattacks.
Old-school killchart: caster, archer, assasin, melee. Casters can hurt your swordsman badly since they have magical attack (that's why discipline is handy), shooters will almost always try to shoot your archers down. Once that's done, enemies with poisons and debuff, than the rest. If you have Zombie-Skeleton, Orc-Goblin warbands on the right, pick the first with your archers, and position your swordsmen to smash the latter first (enemy moves+1 tile inbetween the 2).
You like: Hills, Swamps, Mountains, lakes a lot, since they let you maximise the effectiveness of your swordsman, and let your enemies crawl towards you.
You hate: Forests, plains. The first because they protect enemies from shots, the second because enemies will move quickly.
One more thing:
You may sometimes want to set the combat for quick-resolve (scroll icon next to the double swords). This will not only yield surprisingly good results at times (or not), but I also think the AI tends to award more medals that way. I once had a bowman with 1 fire award and 2 eagle eye awards, now he was a monster. I got it by quick-combating.
That should get you started, I'm unsure if it works mid or late game grand-campaign wise, but it definitely works in the beginning.
Good luck!
Post edited March 02, 2013 by Jabloko