GabiMoro: In a battle where you have superior archers (range attack creatures) don't move towards the enemy. Let him come to you. Use "slow" spell if you can.
Like DarrkPhoenix said: use your archers and guard them well. Before the battle split your troops (ex: 14 pikemen in: 1, 10, 1, 1, 1). Move all single creatures near your archers (surround them) so they won't be attacked by enemy and forced to fight in melee. Protect your archers as much as you can.
Use "wait". Archers do half damage when they shoot far away troops (the arrow is broken). If the enemy can't get you in the next turn, then let your archers wait, enemy move closer, then shoot with full damage.
Same with melee troops. Wait with all your army, 5 dwarves come closer, attack the 5 dwarves with 1 pikeman, dwarves retaliate and the 1 pikeman dies, then attack with 10 pikemen, 1 dwarf dies, and the remaining dwarves don't retaliate because they do that only once per turn and they did that already on 1 pikeman.
Next turn begins: Attack with 1 pikeman, dwaves rataliate, then with 10 pikemen, another dwarf dies and no retaliation.
You killed 2 dwarves and you only lost 2 pikemen, which are weaker creatures.
I hope you got the point.
Good hero skills are very important in battle: try to get offence, armorer and archery (if you have 2 types of range attack creatures in your army).
That's a great post. I've never really understood the value of wait and I've been playing this game since HOMM 1 originally came out.
Strongly agree, also, with using slow and keeping archers safe by surrounding. I often use the skill "tactics" to do this when I'm lucky enough to get it. Great skill even for a caster hero.
Another tactic I recommend is getting a fast character of some type and/or hasting a character, then running him between and around and behind the advancing enemy. Count up his movement by hex and keep him just out of reach while your archers lay waste to the pursuing enemy. Take care to keep your "follow the leader" decoy from getting too close to your other troops, so the enemy doesn't decide to go for them instead. Use the time created to move your other troops to surround your archers.
I tend to put my archers 1st and 3rd from the top slots so I can move them together quickly when necessary. The reason I don't put them 1st and 2nd position? Meteor shower. Hit and run fights in which the enemy can zap you with a single powerful spell and then run away can be damaging over time.
Make getting earth magic and air magic skills a priority. Don't miss great skills to do it, but once you have a good complement of them, make getting expert status in those schools of magic a priority. Earth will let you cast cheap army-wide slow to delay your enemy so your archers can decimate them before they come near, while air will let you, once the enemy is close enough to strike in the next turn, cast cheap army-wide haste so your slow archers can get in a last volley before the enemy's melee troops start pounding them. Haste is also great for taking out enemy archers so your enemy cannot damage you (or damage you much) before his slowed footsoldiers reach you. Properly managed slow and haste are often enough to win a battle against far superior troops.
Not to mention, the highest levels of the earth (resurrection, town portal, implosion, earth elemental) and air (fly, dimension door) top-level spells are enormously powerful, all but earth elemental almost assuring all by themselves that you've won the game. And earth elemental is the only good summoned elemental and a great help in preserving your troops or even turning hopeless battles around with minimal troop loss.