Moving around the battlefield and order of turns | Combat The Banner Saga Guide
Last update: 11 May 2016
The game explains moving around the battlefield during the battle in the prologue. To remind you blue tiles are the "standard" range of a unit, while the yellow ones are the extended range - to move there, you must spend some willpower points. It means that the yellow tiles become visible only when the selected hero has enough willpower. You should use them only when you're determined to get rid of a specific opponent quickly. If you don't need to do it, you should spend the points on other things.
When you plan your next moves, you should check the range of enemy units - if you stand on a tile right out of opponent's range, they won't be able to attack you during their turn. Moving around is not obligatory so you may stay in one place during your turn. It's highly advised for archers (they may get an attack bonus for staying in place) and warriors with shields (they can use special abilities that improve defence).
Note - characters that use spears (e.g. Ludin) don't have to stand directly next to an enemy because they may also attack diagonally. It's worth keeping in mind, especially when standing in such a place might give the character a better protection or prevent them from the enemy's counter.
Right before most battles, the game lets you place your units on the battlefield and you shouldn't skip this part because in many cases default placements are completely useless.
If you're dealing with a "regular" battlefield, the area to place your units is usually in the shape of a large rectangle. In that case, you should place giants and good warriors in the first line and weaker characters (especially archers) behind them. Unfortunately, the game sometimes spreads your units around the battlefield, in that case finding the best formation is not so easy. Try to pick places from which your units may attack as quickly as possible (preferably in your first turn) and pay attention to safety of your weakest characters.
Another thing explained in the tutorial is that the sides of the battle take turns and in the beginning the number of units on each side does not affect it. For example, decreasing the number of enemy units from four to two won't make them take their turns half as often. Instead, the two remaining units will be able to take actions twice as often. It's one of the reasons why you should take on the strongest enemy units first - because of that, later in the battle the enemy won't be able to perform strong attacks as often. It changes only when there's only one enemy left on the battlefield and Pillage Mode starts, then all of your party may perform their moves before the enemy's turn comes.
Remember to visit the Heroes screen between battles and plan the order of their turns in the following battles (Turn Order column). You should give the highest priority to the giants (varl) and the strongest warriors, thanks to that you increase their chance to defeat or weaken the enemy units before they even do anything. Put your archers at the very end. It is justified by the fact that the enemies will move closer to your units by that time and you won't even have to move your archers.