(I apologize if this isn't the place to start this, but it's the best place I could think of)
When designing/creating/building a new army book or codex, what are some good rules to follow?
What are good pitfalls to avoid?
How many units should each slot (HQ, Troop, Core, Rare, etc) have in a well constructed book?
How many Unique characters/units would be too many?