I started with Mercurio's 2-step macro for my Elemental Shamans, but ended up tweaking it manually by testing on dummies. The best thing I can suggest is to do the same. The easiest way I found was to play one toon by itself and closely watch things like how many charges you have, Flame Shock timer/cooldown, Earth Shock cooldown, etc.

If you don't care about the hit cap for raiding, you can just reforge everything to haste (or mastery if you already have haste).
If you want to optimize for raiding stats, I recommend askmrrobot.com.