For me, I started with down strokes (thanks to Metallica) and my Rhythm has really improved. Like Dragonforce says.... the Black Album was secretly made to teach you guitar. My palm muting technique and down strokes came from playing James's guitar parts.

As for alternate picking..... really got into it once I started to solo and discovered Zakk. I started off with Pentas and worked my way from there.

With Lots and lots and lots of practise! It took me about 2 years to perfect my pinch harmonics..... no real shortcuts...
Just practise and practise and figure out where the harmonics "pings" best on your guitar. Every guitar has it's different sweet spots along the string.

YES! The best "pings" comes from the bridge Humbuckers..... actives if possible. A single Coil pick up CAN produce the harmonics, but if you're doing it Zakk style, you'll need an active humbucker to pull it off well.

You can't perfect harmonics in a single day.......
It took me 2 years and then some........