Sorry if this is a repost, search didn't give any results (cooldown, items, aoe, etc.)
This is useful for stuff like the bombing quests etc, where you have an item that uses an aoe spell with a cooldown.
1. Put it on your action bar.
2. Right click item and get the AoE targeting circle up.
3. Click the ground where you want to target it and click your actionbar key right after.
4. If done correctly you now have your AoE target circle up again!
5. Click and fire the same spell twice.