Do casters attack with there charm that has spell damage or attack with there weapon?

also do they use one charm for dmg and another charm for healing?

is the weapon only used to add stats etc..?

caster attack with the charm that has the spell damage. Sometimes they might attack with their wpn if they run out of mana and the monster is almost dead.

You use 1 charm for attacking and then another for healing.

A weapon and a armor are used to add stats. You attack charm can also add stats as well, but you want to make sure it has enhacned effect on it.

Todd is 100% right, but this guide can answer all of your questions and more: http://forums.d2jsp.org/index.php?showtopic=30551054&f=74

Thanks this helped alot.

Also, how do you use mana regen items?
Do you just put them on after battle..or during?

Yeah, they only work when you're not in combat though. So just get a weapon, robe and charm with some mana regen and keep them in your inventory, then switch gear when you run out of mana