So, i've attempted to learn to shred numerous times. I've failed every time. Now i'm not looking to use this to sit there and play scales and arpeggios up and down endlessly. I want to learn how to do it so that I can add a new aspect to my playing and become more versitile (not sure on spelling). Each time i've tried to learn it i've been told to practice a lot, use a metronome, and go slowly. The problem is I don't know WHAT to practice.

So could someone give me some nice exercises for building speed and accuracy in alternate picking, letato, sweeping, string skipping, tapping, etc?

And also when sweeping are you supposed to mute the strings with your right hand or not?

If so how do you do that?

For Alternate picking - Shred like me (search it on youtube, and theres a tab for it on UG)

Serrping/arpeggios = arpeggios from hell or just pick some out of songs you like.

Tapping - The solo out of ;To the Rats' by Trivium.
Joe Satriani is the king of legato, maybe look at "Crushing Day", very good song.

Michael Angelo Batio has some lessons (tabs are on UG, I believe) that teach you good economy-picking, string-skipping, and--of course-- sweeping.

"Psalms of Lydia" by Nevermore has some sweeping exercises, and just check out a bunch of Youtube videos so you can really get the idea of how to sweep.
find songs that sound like what you want to play and learn them.
just practice songs you like, and the theory/scales/arpeggios will come out of it.