Put strongest character first (most lp, shield pref. w/ slash evasion etc.) mainly the guy (or gal) w/ most lp.
Keep main character in the back. once he/she/it is dead, the game is over!
Attacks don't have to happen in order! use recovery spells or any other turn first, save the one's you want to comb. This let's the enemy use up its turs, making combos easier to pull off.
Don't waste weapon endurance on weak enemies. Just melee 'em death.
Get in the habit of saving before every mission.
Upgrade weapons etc. at blacksmith using mostly materials the item is made of. don't let ED get to high or item will lose abilities.