To understand the purpose of guitar strumming techniques we must first learn how to play the rhythm. Rhythm is an important part of any song. Without it it is impossible to develop any flavor in a song and it becomes much more difficult for the listener to understand it. So it is imperative to know how to play the rhythm.
Several guitar strumming techniques are available, but you should develop your own style. If you look at Al Di Meola, John Mclaughlin, Eric Clapton and other guitar masters you will notice they all have their own style. The easiest part to personalise is your strumming technique as it doesn’t have to be precise, and it doesn’t have to copy what is written in the rhythm pattern.
For the rhythm pattern there are a few good ways to remember it. First of all you should always tap your foot to keep the rhythm while you’re playing. When you have a bit more experience with that you can even tap the main beats a little bit harder than the others. Another method is to clap your hands, but this will keep you from playing while doing it. So I recommend tapping your foot at all times.
The most important skill you need to acquire is a technique I call counter-rhythm, which is basically tapping your foot and playing the counter measures of the main beats. Most guitar players change the tapping of their foot to adjust to the new rhythm, but this is a mistake.
A few standard guitar strumming techniques are the simple brush-type up and down movement meant to play the whole chord in one slice, the rasgueado(the typical flamenco technique) and something I call the ‘trio’, which means doing a fast up-down-up or down-up-down motion on all the strings, creating a galloping effect to add flavour to the rhythm.