Rush and claim as many factories as you can while using ZOC to deny the enemy factories. Even if an enemy captures a factory, you can still re-capture it on the next turn and gain whatever is left in it, including the enemy infantry inside. Blocking the hexes around factories will prevent the enemy from deploying their units while you work to capture it for yourself. Whether you win or lose the stage is usually determined by the first few turns of factory conquest. There is a small number of stages where it is more efficient to capture the enemy's Base instead of claiming factories.
Retreat your injured units into factories or repair with Teknik units, while using ZOC to deny enemy retreat. The best way to prevent enemy retreat is to kill the unit.
Surround enemies for the battle support bonus, allowing you to take down powerful enemies while suffering minimal losses. Remember that you need the enemy unit pinned down in two parallel hexes to cut its defense and attack in half. For example, an enemy surrounded on its N and S hexes, NW and SE hexes, or its SW and NE hexes. Any unit can provide support, even airtriggers and pelicans that don't have an attack, so use them for supporting whenever needed. An effective strategy is to move a unit next to an enemy without attacking it (press the Abort button), then attack it from the opposite side for the support bonus. Air units are especially useful for getting around behind an enemy for support attacks due to their high movement range.
All other standard tactical level strategies apply: Use terrain to your advantage, attack targets with units they are weak against, distract the CPU with bait units, keep vulnerable and necessary units out of enemy attack range, hold enemies off in chokepoints, etc. Bait units include infantry and transports like mules and charlies that no longer have any purpose, but also anti-air units that no longer have any air units left to kill, like falcons, hawkeyes, and seekers. These are tactics that are useful in almost any tactical level game.
You don't ever have to save/reload abuse to complete the game. Don't make yourself miserable save/reload abusing to get combat results or CPU behavior, instead improve your strategy. I did not save/reload abuse at all to finish this guide and this walkthrough doesn't rely on it or ask you to do it. There are random elements to the CPU's behavior, but I have tried to point out how to react to the most common random parts of a stage.