What is it?
Alternate picking is arguably one of the most used right hand techniques on the guitar and is the most common method of plectrum playing.
Alternate picking means that the string is alternately picked, steadily and evenly, from above (downstroke ) or below (upstroke V).
How to play it
You pick the first note with down stroke and the next note up stroke and so on. It's important that both hands are synchronized, start slow and only gradually increase the tempo.
The pick motion should came from the wrist, not from the elbow or the joint of the thumb and finger.
In the easy example below alternate picking is used on single string.
In the example below alternate picking is used on A pentatonic scale.
Here the technique is used on a fast lick.