What's the best way to keep your MP up as a spellcaster?

[Mikita]

On long fights, Lucid Dreaming should be used as soon as it's ready from the last time you use it.
Keep it on cooldown.

+1.
I wouldn't save Lucid Dreaming for when MP is almost dry. On big boss fights or longer solo story fights, I usually start using it when my MP is at about 75% and then keep it on cooldown to avoid having to worry about MP running low.

I'll try to mostly save my Verraise for when all healers are dead or if we're running really low on DPSes. Otherwise I'll let the rezzing for the healers when they're still in.

Actually, as a WHM main, I really appreciate when RDMs (especially with Dualcast) or SMNs help with raises. Having that support lets us focus on keeping the remaining people alive.
For healers Swiftcast is precious and if it's on cooldown, then the long cast time of Raise is one of most dangerous things to do.