My setup

I am going to explain how I went about setting up multiple accounts allowing me to play both accounts at once.  My method is a bit different than much of what you would find on http://www.dual-boxing.com .  Which by the way is a great resource for all things multiboxing.  The site has sections devoted to software and hardware that helps you cascade keystrokes allowing you to have the synchronized shaman lightning spam that makes multiboxing so infamous.  


Essential Addon

First I would suggest an addon called Hydra - multiboxing leveling helper.  http://www.curse.com/addons/wow/hydra this addon allows you to automate as many tasks as possible allowing you to focus on controlling your main character and swapping to your second character only when needed.  My main purpose for it is the significantly improved follow command.  Basically you set up one character as the leader, create a macro that tells the party to follow you and your other characters follow.  Doing it this way keeps you from losing your second character as much as you would otherwise.  

Hydra also allows you to cascade whispers to your second character and can be set up to allow the second character to accept group invites from the leader.  This is very helpful if you are running two copies of wow on the same machine and one screen is behind the other one.  With this setup you could log into two copies of World of Warcraft.  Invite the second account to a group.  Hit your follow me macro, and take off to the instance.  Another neat feature is Hydra will automatically have your second account mount up if you mount up on your leader.  It will also chose a flying mount if your leader does.  Making things very convenient.  


Necessary Software

Another bit of software I cannot live without is Input Director http://www.inputdirector.com/ Input Director is an application that allows you to control multiple computers with a single keyboard and mouse.  Think of it as a sort of software KVM.  On my desk I have two monitors, one keyboard and once mouse.  Under my desk I have two computers.  Both are running flavors of windows.  One runs Windows 7 and the other is running XP.  Hopefully both will siib be running Windows 7.  

Basically when I move my mouse from one screen to the next, I go from controlling the first computer to the second computer.  Input Director hides the mouse pointer on the first computer when you are controlling the second computer.   I find this setup so convenient that I now always have my desk set up this way regardless of what I am doing, gaming or what not.  It is particularly helpful when you need to move files between shared locations on the network.  

There are other software options that function in a similar way to Input Director.  The others I have tried all seem to suffer to mouse look issues.  Basically they work perfectly when on the Windows Desktop, but when you are in a game suddenly your character will start spinning around like you are mouse-turning on speed.  Additionally the author of Input Director, Shane, is incredibly helpful.  Many years ago he provided me a custom built debug version of the application to allow me to troubleshoot a self inflicted network issue that was making input director behave oddly.  How many software publishers would do that for you for software provided for free?