Focus targeting and you
The long-awaited guide to focus targeting and macros, written by Huller/Khaevil/Stomples.
First, in key bindings bind a key to:
Focus Target – will set current main target as focus target
Target Focus – will target your focus target as your main target

Focus target is used to have two target windows:

Standard strategy is to have all your spells macroed, for example:
#showtooltip
/stopcasting
/cast [modifier:alt, target=focus][nomodifier] Counterspell
That way you can keep killing while watching that healer or whatever in the focus target, when they start a heal hit the macro with the modifier and it’ll counterspell that healer instead.
For instance, if you use the above macro and hold alt while hitting your counterspell button, it counterspells the focus target. But if you do not hit alt, it counterspells your current target.
Post questions if you have any please.
EDIT: I am told CC focus is a good mod for making quick focus target macros. Macroing is certainly not my forte so I’ll be trying this out sometime today and Monday.