And then there's the most important and nebulous thing in the game, Alignment. Alignment is a number that ranges from 0 to 100; 0 means completely Chaotic, 100 means completely Lawful. There are a variety of classes that need very particular alignments to change into, with the general rule that warrior classes run the gamut of alignments, casters tend to be lower alignment, and healers tend to be higher alignment. Male lawful classes include Knights and Paladins, neutral classes are Fencers, Swordmasters, Phalanx, Cataphracts, Doll Masters, and Enchanters, chaotic classes include Wizards, Archmages, Beast Tamers, Beast Masters, Berserkers, Black Knights, Ninja, and Ninja Masters. Female lawful classes include Clerics, Priests, Valkyries, and Freya, neutral classes are Archers, Dianas, Dragon Tamers, and Dragon Masters, chaotic classes include Sorceresses, Sirens, and Witches. There's also a variety of different monsters and demi-humans that also have their own alignments.
When you create a unit in OB64, you select up to 5 normal sized characters, or you can substitute a large size character such as a dragon, a golem, or other varieties of beasts in place of two normal sized characters, meaning that it can be any combination of 5 normal, 3 normal and 1 large, or 1 normal and 2 large in a group. Whenever you form a new unit, the characters alignment will try to average out with each other. This means little if it's a full high or low alignment unit, but if it's mixed, they will start to even out towards neutral at first, though this can be moved along somewhat in one direction or another depending on your actions.
To clarify that last point, lets talk about what causes alignment to move in one direction or another. To increase your alignment, it helps to keep the units level lower than who they are fighting. It also helps to fight units that are mostly lower in alignment than they are. Finally, the method of attack helps, too; choosing a battle strategy of Attack Strongest and refusing to give chase to units that have lost their leaders will keep their alignment from lowering.
Decreasing alignment, though, requires the opposite effect. Allow these units to have a higher level than the enemies they are fighting, and target units full of high alignment enemies. Choose the battle strategy of Attack Weakest, and hunt down and destroy the enemy. Keep a neutral alignment is much more difficult, though, as you are likely to see many ups and downs with them depending on what you do. The best attack strategy in this situation is Attack Leader, which will simply attempt to attack the leader with everyone that can.
Forming good units, though, can be difficult to do. Some of the most obvious are the Beast/Dragon/Golem units, where a single tamer leads two of the larger monsters. The most effective of such units tends to be one Beast Tamer/2 Hellhound unit, as well as the Doll Master/2 Golem unit, and the Dragon Tamer/2 Dragon unit. There are variations, though; substitute a Wyrm for one of the Hellhounds will be slightly weaker early on, but gets a breath attack when the Wyrm upgrades later in the game. The types of dragons are also of concern; Young Dragons upgrade to the appropriate colored dragon depending on the dragon's patron element, though if you carefully cultivate their alignment and stats, they can also become powerful Black or White Dragons as well. This also doesn't take into account the possibility of other unit configurations, such as the 3 Vultan/Gryphon or 3 Raven/Wyrm unit, or a particularly nasty combo I thought up recently of Cleric/Golem/Dragon.
But those are just for beast-type units. What about others? You generally want to mix like with like where alignments are concerned. This unfortunately means you'll be light on magic on high-alignment units, as only the Valkyrie gets magic naturally without equipping an elemental weapon, and it's not that strong. Similarly, you'll be light on healing on low-alignment units. A typical high-alignment unit might have 1 or 2 Knights, a Fencer, Phalanx, or Valkyrie, an Archer, and a Cleric, situated to take advantage of the most attacks and highest damage available. A typical low-alignment unit might have a mix of Berserkers and Ninja in the front protecting a Wizard and Sorceress in the back.
But it's also up to your imagination. An Archer in the center with Valkyries in the corners fights equally well no matter which direction they are attacked from. Other concerns include those that can use magic and which spells they can use, as there is such a thing as combination magic. There's also concerns such as the middle row: there are very few classes that can fight effectively from the middle row. The Archer, Doll Master, and Beast Tamer are amongst the few that have their best attacks from there; most classes will want to be in the front (physical classes) or back (magical classes) for more and stronger attacks.
The final consideration for forming a unit is their items. Specifically those held by the unit and used on the map. The number of slots that can hold items is determined by the classes that make up the unit; most physical classes can hold 2 items, while most magical classes can only hold 1, and large-sized can generally hold 3 items. Depending on how much space you have, you'll want a healthy mix of healing items, both those that heal HP and those that heal stamina. Heal Leaves and Power Fruit are good at the start, though money is tight and you won't be able to fully kit everyone out at first. As you continue through the game, you'll be able to afford to fill every space and use more powerful items: Heal Seeds and Packs (300 HP to 1 or 150 HP to all) and Angel Fruits for almost full stamina recovery. Of course, there's also passive items, like the Ansate Cross which reverses the gender of promoted soldiers (so male leaders promote soldiers to Amazons, and female leaders promote soldiers to Fighters), and rarer, more expensive items like the Resurrection Altar.
There's so much more I could probably say, but I think I've mentioned all that I can for the moment. I'll leave it at this for now...