1) When grinding for EXP and DCT and unlocking potentials and Character Missions, temporarily switch to EASY MODE when doing the missions. If you are having a tough time S Ranking the last mission of chapter, you *may* wish to temporarily switch the difficulty to EASY, (though I consider this cheating, but to each their own…). Unlocking Character missions require using the squad member at least 35 times. Try to have at lease one person be 3rd tier level of a class, so you that you have one of everything. Kurt will probably be able to be a MASTER of all classes (requires 3 tier for each class and unlocking the 3 potentials / class)
2) Always deploy the CP giving senior level veterans. (They have the star like medal beside their name). Assign the CP stars to either a shock trooper or gunner and let them defend your main base. Avoid using the CP star on the tank driver, as you often need to retreat the tank and move it to another stage. If you have characters that are forced to be deployed, you make wish to make them the CP
3) When doing story missions, try to make characters who are specialized — like giving a 3rd tier scout the +20 AP accessory, makes the scout cover 3/4 of the map! Other examples, giving a +20 vs Personnel (Golden Bullet) to a shock trooper will make them very powerful enough to eliminate strong knights, bosses and excellent at defending bases.
4) Learn the classes and characters’ strengths and weakness: Try to make at least one mortar lancer, and one anti tank sniper for the rare occasions they are useful. For example: Scouts are weak to interception fire, so if you give them extra armor, they maybe more easily able to take a base. Shocktroopers have very poor AP, so it is better to use your bases to move them. Fencers are not good defenders, and are only useful when attacking at CLOSE RANGE (near a base). Lancers are quite overpowered at the end game (equal to a sniper actually), especially if you give them the extra accuracy accessory and use a character like Gloria who has high accuracy to start with. Some characters like Zahar and Susie have crippling Character Potentials, so do not use them until your morale is 4 or higher (or simply just use them unless they are defending bases). Riela gets a crippling Character Potential, for a few chapters, so until that time use Alysse or some other Valkyria based character. Alysse has no real weaknesses, so I prefer her over Riela.
5) Learn the game mechanics: Bosses and especially Valkrias should be attacked from behind. Using grenades means you will not be counter attacked. If scouts have an extra grenade, then they will be able to usually clear the troops out of the base and not be attacked. Use the grenades to push them out of the base, that way you can take it even if they did not die. Use interception fire from enemies to kill their own troops if you are invulnerable or a tank, if you NEED to save CP for an S rank.