OK, let's get this started!
First a few basic tactical concepts that apply to any conventional battle on land/sea/air.
Initial Deployment is Critical
Once a force engages an enemy it's ability to move and reposition is severely limited. Likewise, if a unit is spending all it's time moving to a new position because it was misdeployed it is not helping the attack. Therefore, a commander needs to "get it right" at the beginning.
Maximize Firepower
If a unit doesn't fire, it can't kill the enemy. The more shots you take, the more damage a unit will do. Therefore, the maximum damage a force can deliver is to have every unit fire every fire phase! Of course, it is impossible to achieve this in most cases, but it is the goal of positioning the units. More shots taken with the most firepower available, the more enemy casualties that will be inflicted.
Unit Coherence
In order for a unit to maintain coherence, it must be close enough together that all element can directly support one another. That means supporting fire on the same targets. For example, say there are two squads with a range of 12 each. Once those two squads are more then 24 hexes apart, it is no longer possible for them to fire on the same enemy unit under any circumstances, therefore they can't support each other. Once unit coherence is lost, each individual element can/will be destroyed in detail. Intervening terrain can also destroy unit coherence. In a city fight, units only a few hexes apart can be isolated. Use this concept to maintain our force integrity, and use it against the enemy by isolating and destroying their unit coherence.
These concepts are all fairly obvious, but they are often forgotten in the heat of battle. However, following these basic principles of war will lead us to Victory!