well, if you absolutely need the bleeds to be at a minimum...
(1) i've read (although i've never really tried) that you can use earphones, then use ear muffs (is that what they're called? -- those things that look like headphones, but there are no speakers inside). or use something like the VIC FIRTH POWERED STEREO ISOLATION HEADPHONES. (I just realized starfugger already suggested this...)
(2) lower the volume of the music going to the headphones, or lower the tracks you don't need to listen to.
(3) if you're using a click track, use a sound with less high frequency content. logic pro uses a sound called klopfgeist, which is pretty much like an 808 kick pitched upwards. it doesn't bleed as much as cowbell, sidestick, or those click sounds from roland sequencers.
hope this helps, although i agree with mikep and kedysanchez' points.