It does take quite a bit getting used to IMO. When I first started, I would check these forums every day just to find ANY way to make things easier/faster. You'll learn more macros than you probably ever thought possible before multiboxing. You'll start thinking of the game in a totally different way. All in all, I would suggest looking for anything in your current setup that seems "slow" or "inefficient" and looking for ways to improve. Some common things that seem inefficient:

- Typing Macros in every characters screen (Solution: Use a text editor offline to write your macros right into the macros.txt file in WoW)
- Main characters bag fills up too quickly (Solution: Use keyclones built in BOOBS and PiP to switch your "main" quickly when their bag fills up)
- Changing "mains" is clunky (Solution: look into using /focus macros for all your spells including /follow focus so that you can switch mains quickly)

Stuff like this made my experience a lot smoother and enjoyable.