Really, the only sure fire way is to move to a place where you simply can't find opiates, ideally a place that you don't speak the native language. It really is that hard for most of us...good luck...
When I quit using for a few years, one day woke up and realized that it wasn't getting me high anymore and I needed to stop, of course that was a fluke occurance, but that is usually what happens when some of us quit. No methadone, no tapering...just man up, enjoy the 3-10 days of hell, and move on.
But cutting off your access to opiates is the only thing that will keep them out of mind, at least to the point where you're not thinking about them EVERY time a little boredom creeps into one's life.
Go teach english is Mexico or Russia, something like that...do it for a year and you should be feeling much better about yourself. Yeah, you may slip up when you're close to old dealers/dope spots, but then again you DON'T have to return if quitting is that important to you.
On the other hand, a dope fiend can find his fix wherever he or she is...but if you make it EXTEMEMLY hard to do, you can beat the cravings...again, best of luck!