In this riff, we have a good mix of alternate picking, palm muting, and legato.
First thing we should note, is how on every single pull-off you do, you'll be using a downstroke. Make sure you keep that pattern throughout so we can stay consistent with our picking. Besides those downstrokes for the pull-offs, we'll be using strictly alternate picking. Just in case you get lost with how you should be picking, look under your tab to find the appropriate pickstroke symbols.
Next thing to note, is how when we're not pulling-off, we're palm muting on the open strings using alternate picking. Look for the "P.M." symbols which indicate palm muting. You'll see them throughout this tutorial.
One other thing I want to advise you on...Watch out for open string noise! Since this is a fast, aggressive riff, it can sometimes be easy to get unnecessarily aggressive with our pull-offs, causing our fingers to hit adjacent strings. Practice this slowly to make sure your form is clean, then gradually get faster.