I have been in a few groups where we actually "practiced" getting off certain group HOs. The shaman knew that if the scout started, then the mage went - then everyone else finished as the starter wheel indicated - we'd tend to get a nice buff and maybe a big group heal. We practiced that one for fighting tought ^^ mobs and bosses, etc.
Another type of HO started w/ the fighter, then the Healer doing strike, then the mage doing lightning - then we got a wheel that tended to do big damage. That was for speeding up fights.
So much depends on who starts the HO and then who goes *next*. You can't pick your exact HO, but you can angle it toward one set of three versus another set of three. Oh, and a scout who is really on the ball can use a Coin skill to swap a dumb HO for a shot at a new and better one. I've yet to see many scouts doing this, however. Very few players bother to master HOs, and I've only just begun to myself.
I wish I remembered exactly how we did it. That was my best group HO experience. I can tell you, with a patient, competent group doing smart HOs, a group can take down a really big named mob. W/out this... expect wipes.
It's really hard to get group HOs off. It gets tedious, and a lot of players get bored or frustrated. Many players simply don't have the discipline to do it. Google "eq2 heroic opportunity guides". And it's not always good. Sometimes it's best to just let people nuke, heal and whack, whatever.
Oh, I found the link I was looking for! Try this - it's really good: http://www.gnorrath.com/
Just be aware that group HOing doesn't happen much, at least from my exp. The tank often solo HOs in a group, and that's about it.
Like another poster said, for melee classes chain-hoing is a great idea while soloing (also for healers soloing). It's really easy, as they outlined, and do look into macroing them.