Gonna share my healing macro. Using the priest spell Flash Heal as example here. Just change that to wich ever spell u want. U can add ranks as well ofc.

#showtooltip Flash Heal
/cast [modifier:alt,target=player] [target=mouseover,exists,help] [exists,help] [target=targettarget,exists,help] [ ] Flash Heal

What this little cuty does is:
1. If u have your mousepointer over a friendly target in your raid frames it will cast the spell Flash Heal on your target.
2. If u don't have your mousepointer over a friendly raidframe target it will cast Flash Heal on your normal target (ie the target you get if you click on somone, say that you have your maintank as target).
3. If u don't have your mousepointer over a friendly raidframe target and your "normal" target is a hostile mob, it will cast Flash Heal on that mobs target.
Very handy for bosses wich switch targets like Solarian or like for instance you have the boss targeted and you're healing the maintank with this macro, and some dpser noob overagros. Without you changing a thing the macro will now heal the overagroing noob.
4. If you have the ALT key pressed at the same time as you press this macro you will cast Flash Heal on yourself. Of course you can change the key to ctrl or shift or whatever you want.
5. If you dont have any target and you dont have your mouse over any raidframe it will just cast the spell as normal.

Dont be a "clicker".... 

Yea, pretty nice with mousover