F3 > F4 > F4 > F1 > F4 > F4. That's the core rotation they should be fitting into every Astral Fire phase.

You can spice it up with spell speed and cooldowns in your opener, but beginner BLMs should just focus on nailing enochian management.

Other tips:
Always re-apply thunder before Blizz IV, unless you think Enochian will drop off. Ideally refreshing Enochian is the last thing you want to do in Umbral Ice.
Thundercloud procs are a straight dps increase over F4, however you want to avoid clipping the dot by too much (ie. two thundercloud procs back-to-back is a dps loss. You want it to tick 3+ times).
Sharpcast should always be paired with a Fire 1 at the beginning of Astral Fire (F3 > Sharpcast F1)
Ley lines should be used to get the most out of Raging Strikes, and then whenever it's up while you're waiting on RS. Just don't be silly with the placement, it's not an excuse to stand in fire.
I like to open with B3 > T2 > F3. Umbral Ice speeds up the cast of F3 and you'll be at full MP for your opener. But some BLMs don't bother.