so here is the classic problem, how do i get rid of the background so that the guy remains ?

layermask ?
path tool ?
highpassfilter ?
channel mixer ?
quickmask ?
eraser tool ?
etc.

the t-shirt part is probably the easiest but the dark skin against the dark background is kind of tricky

what is the best and most effective technique for that particular picture ?
your opinions and secret techniques pls

I would use the path tool and finish the fine details with a quickmask. Relatively quick work even counting the time to zoom in to the 2-3 pixel range for a neat job.

If you just want the guy I can do it in less than 3 or 4 minutes with Xara Designer

nah GMS, just curious about Gimp techniques

i like layermasks, 'tstandiford' has conditioned me forever with his tutorials i guess, lol

so i rendered the picture in four parts
part one: body with a standard layermask (you know, b/w copy, values)
part two and three: selected the arms with the path tool and used a selection layermask
part four: bits of the dreadlocks and beard (painted the layermask by hand)

Nice technique, Esper!
For the same task in my recent post here I used Foreground select tool and then Fuzzy select tool to remove what is left from background (I usually set threshold to 20-25 and press Shift key to add to selection). In the end I always alpha select, shrink by 1 pixel and invert-clear to make the edges clean. Fast method for less accuracy and takes about 4-5 minutes.

interesting K1te !

i tried it but used the foreground selection tool to turn the selection into a layermask, because i felt that would give me more control
it was indeed pretty quick, but there was a look of cleaning up to do, with the fuzzy select tool

getting the edges clean is always the biggest problem, so your technique with shrinking by 1px is a good choice i think