Keep astral power out of combat.

[PhillipPhillips]

As a boomkin, when you are out of combat, usually astral power drains over time. This is totally negated by switching in and out of bear form as long as you are out of combat. Useful for gaining 100 astral power pre-boss and spamming bear form until boss starts to get free starsurges.

TL;DR Use bear form constantly out of combat to save astral power.