Basics of Strumming: Downstrokes 

There are some basic rules to understand before learning to strum on the guitar: Downbeats are played by strumming down towards the ground. These are called Downstrokes. Unlike our single notes, Strumming requires us to use our elbow, rather than our wrist, as the primary mechanism of moving through the stings. 

The goal when strumming chords is to move the arm quickly through the strings so the pick hits each string at the same time. With a downstroke, my goal is to establish the chord, by playing all of the strings that belong to each chord shape. This will vary between four to all six of my strings depending on the chord, and I want to adjust my strumming hand position according to each chord. 

When strumming, Make sure the arm is flat across the top of the guitar, with no bend in my wrist. Start my arm above the lowest string of the chord, and let the elbow fall across the strings with my wrist following the motion of my elbow. It is very important to keep the entire strumming arm loose and relaxed and not force your way through the strings. I should let the natural weight of my hand and the pull of gravity move my arm through the strings rather than forcing it through the strings. This will result in a harsh sounding strum. The strum should finish with the arm at a 90-degree angle, resting near the bridge, with the thumb pointed towards the ground. 

Basics of Strumming: Upstrokes 

As we learned that downstrokes are played primarily on downbeats, our Upstrokes are strummed upward towards the sky primarily on upbeats. This allows our hand to work like a pendulum, strumming the guitar twice, down and up, for each downward motion. 

While downstrokes are designed to establish the entire chord, an upstroke is unique in that it will sound uneven if I hit all of the strings of each chord on the upstroke. Instead, it is best to split the chord into halves, with the upstroke only playing the top 3 strings of each chord shape. Again, this will vary slightly depending on the chord being played. It is also very important to activate the wrist in a lateral snapping motion moving upward as the hand approaches the strings. My elbow is still the primary joint that directs the strumming motion, but my wrist allows me to only hit the top half of the strings as I follow through with the elbow and prepare for the next downstroke.