First things first - how do you hold this pick thing? Although picks come in all shapes and sizes, they mostly work the same.
First, hold out your strumming hand like you're making a thumbs-up sign. You fingers curl in toward your palm. Your thumb is vertical.
With your fingers all curled in alongside one another, place the pick flat on the side of your index finger. The pointy end of the pick should be perpendicular to your fingertip, and the point of the pick should roughly line up with the bottom of your index fingernail.
Now, just bring your thumb down on top of the pick. The pick should stick out past your curled fingers a bit-you'll have to experiment to find the perfect spot for your pick. The less point you reveal beyond your fingers, the faster you'll be able to play. But, also, the more precise you'll have to be. When you're just starting out, try to find a middle place that feels stable.
Once you have a handle on your pick, you're ready to get strumming.
Hold your guitar like you normally do. Your strumming hand hangs down over the front of the guitar around the soundhole.
Strumming down feels a lot like your hand is falling. Begin your strum with the pick touching the lowest bass string, and then just let your hand fall and bring your pick across each of the six strings in succession. The sound will go from low to high.
Try this a few times. When you strum, keep your wrist more or less straight so that most of the strumming movement comes from higher up in your forearm near the elbow.
When the downward strum feels comfortable, it's time for you to try the upward strum on for size. Just do everything in reverse-begin on the highest pitched string (the 1st string in guitar parlance), and slowly but steadily bring your pick across each string in succession.
This time, you'll hear each string sound in turn from highest to lowest pitch.
When you are ready, it is time to apply your new found strumming technique to an actual song.
The key with strumming once you've got the basic technique down is to treat your strumming hand like a metronome. Maintain the steady down/up pulse in your hand no matter what. Even when you're not actually striking the strings, like when you're resting in side a measure or something, keep the feeling of down/up going. This will help you stay in time within the song.
Explore what it sounds like when you strum down and then up on every single beat.
Then, draw out more music by leaving out a downward or upward strum every once in a while. It's amazing how much interest you can create just by leaving out a downstroke within an otherwise steady stream of down strums and up strums.
