These are my 3 most useful macros as a lock, Posting them for Polemos and it explains how to use FOCUS in a macro
Banish
#show tooltip
/clearfocus [target=focus,dead]
/clearfocus [modifier:alt]
/stopmacro [noharm]
/focus [target=focus,noexists]
/cast [target=focus] Banish
Banishes your current target and sets your focus on that target. You can now target another mob for DPS and rebanish the 1st just by clicking the macro again without targetting it. If you need to switch to another mob to banish before the 1st one is dead then hold down the alt key when you do it.
You can use the same macro for chain fearing, just replace Banish with Fear on the last line.
Seduction
#showtooltip
/clearfocus [modifier:alt]
/focus [target=focus,noexists]; [target=focus,dead]
/clearfocus [target=focus,help]
/petstay
/petfollow
/cast [pet:succubus,target=focus,exists,harm] Seduction; Seduction [modifier:ctrl] Searing Pain
Start by targeting your seduction target and cluck the macro. You can now re-seduce any time by clicking it again. The macro makes the Succubus move before recasting which breaks the current seduction and then recasts immediately. This means you don't have to wait for the time to run out before recasting. click with alt held to target and seduce a different mob while the 1st is still alive. If your Succubus is in danger from the suduced mob then click with ctrl held to cast searing pain on the mob toget aggro from it then click as normal to seduce again.