Tip 1: Know what your heroes' abilities do and what they're strong at/against. Using an ability at the wrong time in battle can prove to be very costly.

Tip 2: Flanking is extremely important, so make sure that you always do it if possible. Don't let weak troops exposed just to flank as it is not worth it, but if you can do it safely, go for it. Remember that if you flank an enemy and they flank you too, all flanking bonuses are cancelled.

Tip 3: Keep the weak/ranged units at the back: this is pretty much common sense I guess: there are few occasions in which you should send your ranged units to the front line.

Tip 4: Don't rush to bring in Guardians from your alliance: they can indeed prove to be extremely helpful in difficult battles, but it's still beter to fight with your own heroes IF they are not at the maximum level as the XP they gain from battle is more useful for the long run. If you have your heroes maxed and still can't do a good job, recruit solid guardians for your team, but remember that 10% of your loot goes their way

Tip 5: Always have a strategy for the battle: even though you can't control the movement of your troops after launching the attack, you should know how the battle would go for the most part. Anticipate the moves on the battlefield and set up your formation in such a way that the biggest threat is taken care of first and you don't leave any flanking options for your enemy in the long run.

Tip 6: The healer is extremely important: be patient and wait for the mana levels to fill until they can use their healing power. Without a healer, most battles are easily lost.