For the thieves...

[Lone Wolf Leonhart]

Do you try to steal at least once from every type of enemy in the game, or do you just steal from the bosses?

I'm deciding whether or not the frequency I see "Couldn't steal!" is worth it.

[Saber]

I like games where you can go back and steal from enemies. I hate it when there is a 1 of a kind item on an enemy and you can't ever get it cause that part of the world is blocked off. It always happens. My advise is to steal from bosses and maybe consult a guide for missable items.

[Roogle]

You should specifically look up what items that you want to receive as stolen goods, or you should configure your party in a way that leaves the Thief with nothing to do except use Steal without impacting the efficiency of the party.

[Wolf Kanno]

I don't really remember any of the bosses having items worth stealing to be honest. On the other hand there are tons of equipment from normal enemies that net you better items. The best whip and katana are items stolen or dropped from end game enemies. There's also the Death Scythe for Berserkers in the first world and probably a few other items I'm forgetting.