Watch the Strumming online guitar lesson by Vicki Genfan from Acoustic Rhythm Survival Guide
Take some time with this. Take your time working with the 'DOWN-UP' motion, getting it real smooth, keeping your right hand and arm relaxed. Play around with different accents. Stop the video and try your own patterns.
Try accenting some of the 'UP' strokes. This will give you some nice syncopated patterns. If you're more advanced, try doing this in odd time signatures, like 5/4 and 7/8!!NOTE:
You could use this as an additional technique – just using the percussive sound in a break, or intro or outro. Check out this video of mine to see an example of a percussive strum pattern used as an intro for my song, 'Nothing's Gonna Stop Me'
Now, when we bring in actual chords, take time working with the right and left hand muting techniques. The more you're able to strum with a relaxed sense of ease, while simultaneously incorporating the muting techniques, the more dynamic and rhythmic your strumming is going to become. In order to get a totally 'killer' rhythmic strum that is 'tight and clean' you need to really have control over both right and left hand muting. Some of you may need more or less time practicing this to really get it down.
With proficiency of the Right Hand muting, you can go into a purely 'rhythmic' strumming pattern at any point. This gives you endless possibilities for new strumming patterns and ways to embellish a song. TRY IT!
Choose a song you know and find a place you want to add a purely 'rhythmic' strumming break. It could be as an intro, in between two sections, as part of a section (for instance, if you're repeating a chorus at the end of a song, you could use this technique the first time you play it, then come in with the 'sounded chords' for the remaining choruses...) NOTE
about picks (plectrums): Really explore the difference in sound and feel with different picks. Not only different thickness, but there are some very exotic and strange picks made from stone and various other materials. You never know, you may find something that really has a 'just right' feeling when it's in your hand!NOTE
about your timing: Many of us have challenges playing 'IN TIME'. If you are one of those people (and it's to your advantage to be honest about this!) consider taking a drumming class or finding a private teacher, or – if you're self-motivated, then work on it yourself. One of the coolest methods of rhythm study I ever came upon is called 'TakeTina' and was founded by world percussionist, Reinhard Flatischler. Check this out!
Then I encourage you to find somewhere to study.
I can't stress enough to you the importance of a solid rhythmic foundation. Simply practicing with a metronome is nice, but it's only part of the work. You need to develop listening skills, and really learn with your whole body how to keep steady, yet flowing time.