In a nutshell, Keyclone sends the keystrokes to multple programs / sessions simultaneously. I.e. if you are running 2 sessions of WoW, you press the '1' key and it send sends '1' to both sessions.
You then have '1' bound in each session to attack / cast a spell / dance / whatever.
You set one toon up as your main, and just have your alt toon(s) follow the main around. You also set up macros on your alts to focus / assist / accept quests & trades / etc.
Get yourself a suitable UI and addons and your set.

Cheers,
Stealthy