Alternate picking means strict down-up, down-up, even when you change notes or strings. It's the foundation of almost every lead style.
The notes come from A minor pentatonic at the 5th fret: index on fret 5, ring on 7, pinky on 8. Start with two picks per note, then four. The third exercise runs up and down the scale with one pick per note.
Make small motions from the wrist, not the elbow. The pick shouldn't travel far past the string; a couple of millimeters is enough. Hold the pick between thumb and the side of your index finger with only the tip showing.
Accent the first note of each group (marked >) so you can hear where the beat is. Down- and up-strokes should sound the same; if the upstrokes are quieter, you're probably catching the string with too little pick.
The most common mistake is starting each new note with a downstroke out of habit. Don't: the down-up pattern never breaks.
Practice each bar on its own until it's relaxed, then play all three in a loop.
