No More Tears was really the guitar world's introduction to the maniacal, shred crazy Zakk Wylde. He is a monster shredder who, in the Eric Johnson mold, does it primarily with the good ole-fashioned pentatonic scale (and a plethora of pick harmonics!). This song and solo helped cement him the role as Ozzy's sideman, desperately needed in the years following the tragic passing of the one and only Randy Rhoads. Although nobody can ultimately fill those shoes, this song helped move Ozzy's music into the consciousness of a younger generation.
This solo is a pretty classic blues really... There is a LOT of swapping out of the major and minor third as Zakk weaves the tonality between these two. This is common in blues. The solo is mostly D minor pentatonic, with the added b5 (making it a Dmin Blues scale) licks and double stops. He ends the solo with repeating groups of 6, moving up the different forms of the pentatonic scale. Until the last bar - where he simply (harmonically that is!) follows the background chords with Bb Major arpeggio - moving to a CMajor arpeggio. Then the money resolution - bending up to hit the tonic note (D) on the closing chord. It's pretty fast and my picking hand struggled to maintain the closing 4 bars.
Getting the sound
Les Paul loaded with Humbuckers - through a Marshall. The real key though is in double tracking the recording takes.