Wiki:Software[/url].) There's no way to make an in-game macro to send commands to your follower.
What that will do is when you press a key, like '0', it will send it to both windows. On your main you bind that key to nothing, and on your follower you bind the 0 key to a macro something like "/target MainName, /cast Heal". You'll also set up macros to stuff like "/follow MainName", "/script AcceptQuest()" Much more information available here:
http://www.dual-boxing.com/wiki/index.php/Macros
D is not possible, there's no way to automate/macro looting. You'll have to manually loot quest items.
DPS+Healer (warrior+druid) is a very common and easy dual-boxing combination.