Capturing asteroids

I've always wondered what it would take to capture an asteroid into a parking orbit somewhere out beyond GEO (geosynchronous orbit). Such a body would be handy to have nearby in that it would allow us to go out and practice a little prospecting without getting too far away from home. My thoughts on this are often stymied by the fact that it would require a lot more effort than we would be able to muster any time soon to redirect such an asteroid into a friendly co-orbit with the Earth.

Then I noticed this article which seems to indicate that we get visited fairly often by asteroids which drift close enough and just fast enough to get caught in our gravity well for a short time. They suggest that these space rocks may be let in, and eventually let out again, through transient gravitational gateways. These low energy paths are thought to arise out of the chaotic relationships between the various gravitational bodies in the solar system and has been dubbed the interplanetary superhighway.

Incidently, there is an asteroid which is currently sharing a somewhat stable orbit with the Earth. This is the so-called second moon, Cruithne. Unfortunately, it does not remain in the proximity of Earth for very long. It spends most of it's orbit out of phase with the Earth (i.e. lagging or leading the Earth in its orbit).

So anyway, this got me to thinking about capturing asteroids again and I was curious about what would be required to nudge one of these visiting bodies into a more stable orbit. Obviously a lot of this would be dependent upon the characteristics of the asteroid and its orbit. If a favorable candidate could be identified in time, and the B612 foundation has developed a suitable technique for alerting the path of an asteroid, then could we actually capture a whole asteroid and have it conveniently at our disposal?

This sounds like an excellent simulation to run in Orbiter (Hi, Bruce!).