Pretty much cast Starsurge whenever it's up. It's our most powerful nuke, plus it provides whatever eclipse power (and takes advantage of the bonus too I believe) you currently need.
I always make sure to put up Moonfire/Sunfire first, since it can proc the insta-Starsurge, then IS, Starsurge, and either Starfire or Wrath spam depending on which eclipse swing I'm going for. When the DoTs wear off, refresh them, and when Starsurge cool down comes off, recast that as well.