Don't use typical multiboxer software. I'm not using a bundle of mice taped together because it's cool, I'm doing it because it's the only thing I know of that isn't against the EULA. Check the first section for pics of a mouse bundle and my 6 keypads with wooden dowels that allow me to press some of the keys on all 6 of them with less effort and arthritis than trying to do it with your fingers. Petition CCP so we can software multibox - Eve will always be one of the hardest game to multibox due to the need for so much mouse interaction but at least it would be nice to have the same tools that WoW multiboxers have.
Don't mine, especially in high-sec! I mined for months on end in 0.0 without anybody except gankers bugging me, but after 2 days of mining in high-sec I was 3-day banned for "macro use". I guess having a gazillion ospreys looks too suspicious and apparently is a common method used by real macro miners. Plus every other person who sees you will petition you out of sheer ignorance and confusion so GM's probably want to get rid of you whether you're doing anything bad or not.
Remember to fleet up and have one of your pilots as your main issue the fleet warps. Have a separate mouse for that guy, you can connect two mice to the same computer if necessary which allows you to still have that pilot controlled by your mouse bundle. Gate jumping and initial targeting of enemies is the hard part but once you get the hang of using your mouse bundle it's not too bad as long as you have your overview sorted by name or something else that prevents a lot of re-sorting on the fly.
When you get really comfortable doing the ordinary you can tackle the real multiboxing prize: spider tanking. Issue a request for shields with one guy and have everyone else target him via the broadcast link and engage shield/armor transfers. If you can master this (you'll screw up a lot and end up shooting your own guys or healing the enemy at times) be ready to potentially tackle some big complexes by yourself. Spider tanking is not necessary to have a lot of fun multiboxing, passive tank fleets work just fine too.