Information on how and why with macro's

I have been looking into setting it all up on my PC to run a priest(shadow) and a rogue(combat). Everything seems fine and dandy I just need to go through the applications and decide which one is going to be best for me.
However the one thing I can't get my head round it the use of macro's, i mean how do I know what macro's I require. I assume I can leave the normal keys for attacking with the rogue as defaults and then just add maybe ctrl+1 to toggle the attack/spell on the priest. Also I read about problems with having WASD bound, do I just disable the WASD keys on the priest and set it to constant follow?
Also what about the looting? will this require tabbing to the other client to manually loot?

I use hardware to box rather than software, so there may be some things that the software can do which I need to use macros for but you wouldn't, but I'll try and give some examples of when ingame macros might be handy (I also suggest you read the stickies in the macros and addons section).

It's probably something you'll develop as you go along in-game, but there are some fairly standard things.

You'll probably want a /follow macro for your priest and also macros can be used to make things like quest accepting easier.

Heal-wise you might be looking for something like:
/cast [modifier:ctrl,help,target=targettarget,help] Heal

This will cast heal if the ctrl key is held down on your target if it is friendly or your targets target if that is friendly (so if your priest is targeting a mob you can still heal your rogue easily).

For dps you might want something like:
/cast [nochanneling,harm,target=targettarget,harm] Mind Flay

Which will try to cast Mind Flay on you target (if unfriendly) or you targets target, but if you're already casting Mind Flay then it won't interupt it (so you could bind it to a button that you mash on your rogue).

Or use a cast sequence:
/castsequence reset=target/combat Mind Blast, Shadow Word: Pain, Mind Flay, Mind Flay, Mind Flay

so you get one button to dps on your priest.

These were written off the top of my head, so may not work in game, it's just to give a general gist of what you might want to use macros for.

Looting wise you need to tab to loot (as it's done on a mouse click. Meaning collection quests are a pain, but for everything else you can stick it on FFA loot and grab everything with your rogue.

When you (or at least I) multibox, you play as a group, not as a sum of seperate toons.
As such, you need macros to let your toons focus on a shared target, assist, follow, help, etc. eachother with every ability you use.

Try to make a list of what you want to do with your toons and think ahead about how you want to do that in terms of keys, bindings and macros.

Some things you might want to think of;
- Broadcasting WSAD to your clones can break follow
- How do you want to assign a target for a spell, without having to assign targets on individual toons?
- Try FFA loot, and just loot with one toon whenever possible.
- Read all the stickies you can find :)

There is no single best way to set things up. Just get your toons rolling and see what works for you.