Basically, I have to learn a song in college every week to be performed and marked. This week, it's The Rasmus, In The Shadows. Now the thing I'm hving trouble with is working out how the guitarist keeps that harmonic sustained for so long at the beginning of the song.

I can't seem to switch between switching the pickups and picking the harmonic and i'll get marked down for doing it incorrectly so if anyone knows the best way please let me know. Cheers in advance.
Listening to the song i have no idea what you mean. The harmonic isn't sustained at all, its played for about a second then muted/ played again??
It's not muted and played again. The harmonic is sustained and the signal is killed in rhythm. And it's not really a question for those forums as it's a specific song which may require the use of a killswitch or pedal effect and i wondered if anyone in this section knew the sng, figured it was more likely here.
I would try putting a compressor before a killswitch in front of the amp. Not too sure if that would work though.