I hesitate to post this, because you should be a.) reading the stickies, b.) working with what you're "used to" for controlling 1 character, and c.) learning macro/focus/follow basics so that you can create your own best setup. All that said, here's a stripped down macro file that I used a few weeks ago.

MACRO 9 "Invite" Ability_Ambush
/invite Boylbee
/invite Boylcee
/invite Boyldee
/invite Boylston
/invite Altela
END
MACRO 3 "Accept" Ability_Ambush
/script AcceptGroup();
/script AcceptQuest();
/script AcceptTrade();
/script RetrieveCorpse();
END
MACRO 1 "Focus" Ability_Ambush
/focus Boylston
/stopmacro [target=focus, exists, nodead]
/focus Boylbee
/stopmacro [target=focus, exists, nodead]
/focus Boylcee
/stopmacro [target=focus, exists, nodead]
/focus Boyldee
END
MACRO 2 "Follow Focus" Spell_Magic_LesserInvisibilty
/follow focus
END

These three are your basic set focus, follow focus, and invite type keys. Obviously my characters are named Boylston, Boylbee, Boylcee, Boyldee... If you're by yourself, you may want a macro that does "/focus player" so that your attack/heal macros behave in a way that you might want (instead of generating "no target" errors.

Below are some attack and healing macros. The healing ones will heal whoever you are controlling is targeting, unless shift is pressed down as well, in which case it starts every shammy healing themselves. You will need to un-bind Shift-xx from something else to make this work.

MACRO 4 "LB" Spell_Nature_Lightning
/cast [target=focustarget] Lightning Bolt
/target [target=focustarget]
END
MACRO 7 "FS" Spell_Fire_FlameShock
/cast [target=focustarget] Flame Shock
/target [target=focustarget]
END
MACRO 12 "HW-F" Spell_Nature_HealingWaveGreater
/cast [target=player,modifier:shift] Healing Wave;
/cast [target=focus] Healing Wave
END
MACRO 10 "LHW-F" Spell_Nature_HealingWaveGreater
/cast [target=player,modifier:shift] Lesser Healing Wave;
/cast [target=focus] Lesser Healing Wave
END

If you are using the in-game macro editor, simply cut and paste the bolded/middle portions of each of the above. Shammies are a little easier/simpler than other classes, since you can pretty much use the Focus is the Main Character type of macro philosophy represented above. Other classes may want to reserve focus for CC abilities (warlocks, mages, etc), so they have a slightly more complex set of choices with macros.

Hope that helps, but I strongly advise you learn basic macroing and keybinding in addition to the software/hardware methods you are using to broadcast keystrokes-- there's no point going the multibox route if you aren't going to learn what works (and what works for you).

Good luck!

Boylston