It really depends on my build. If I'm focused on meleeing with my mage, I'll usually focus on 1 spell I intend to cast and 1 spell as backup in case it doesn't make sense to go with plan A. If I'm focused on playing and supporting my creatures, I often choose 2 spells I intend to cast. The BM can go either way. The Warlock, Forcemaster, and Priestess tend towards casting 1 spell (after some initial setup). The Wizard tends towards casting 2 spells. I don't have enough experience with the Warlord to say how that will work out for me.