I think of a "dead note" as a note with no pitch. To do this, just play the same way with your "picking" hand and with your "fretting" hand touch the string but don't press down. Make sure it's not over a fret where a harmonic will sound out. Actually the more flesh /fingers you use with your fretting hand the darker the mute will sound.
Hopefully that makes sense....
How do you...? 
