Ya auto hotkey is for people who understand scripting.

KeyClone does the same thing but in a way thats much easier to learn. I would suggest using his program if your just getting started its only 10$ and he supports his tool very well answered all my questions for me with in a few moments.

I would suggest you make 3 folders for world of warcraft. this way you dont have to re-trype your account name each time and you can have different settings and addons for each account.

On keyclone there is a do not pass list aka black list in that area there is an option for "white list" the difference between these two is that if you do not have it set to "white list" it will broadcast every single key on the keyboard. However if you use the "white list" and say you only want to pass keys 1 2 3 4 Q E F and the arrow keys then your 2nd and 3rd accounts will only get those keys passed to them when you hit the button. Very simple way to start triple boxing.

After a while you may want to learn how to make keymaps. This takes the tool to a whole new level. by allowing you to hit 1 key and send a specific command to a select account. makes sheeping and seducing or healing a select target much easier.

mxracer050 posted a good guide found here http://www.dual-boxing.com/forums2/viewtopic.php?t=1767

if you have any questions let me know.

Edit he beat me to it lol.