Watch the Strumming Patterns online guitar lesson by TrueFire from Rhythm Guitar Greatest Hits Vol. 1
First Pattern: For the beginning strummer, you first have to master the 'Down-Up' motion with some fluidity. If this is hard for you, take the time to practice it before trying to play the first strum pattern. Ease and Fluidity are key words here.
Another helpful hint is to count along with your strumming so that each strum has a syllable: 1 & 2 & 3 & 4 &... and just repeat. Your DOWN strokes should be the numbers, 1, 2, 3, 4. Your UP strokes should match with the '&' s.
MAKE SURE YOU CAN MASTER THIS BEFORE MOVING ON!
Bass Strings: As you get better at this – pay attention to which string (4th, 5th or 6th) is playing the root of the chord. You want to try to leave out the low strings that are going to conflict with your chords, for example; D chord root is on the 4th string. Try not to hit the 5th and 6th strings. The C chord has its root on the 5th string, so try to leave out the 6th string. Watch the 'muting' technique in this video segment to give you a head start on this.
Second Pattern: Here we're alternating bass notes in each chord. You want to be sure that you're only hitting one string at a time for the bass note. On the 'strumming' part of this pattern, you'll be doing a 'Down-Up' stroke. Your focus or 'aim' is on the top 4 strings (high E, B, G and D). If you're playing it and it doesn't sound right, check to make sure that you are giving the 'Down' stroke a bit more accent than the 'Up' stroke.
Third Pattern (Reggae): The important thing here is mastering the 'Palm Mute' with your right hand. Be sure that you are really muting all the strings and that you hear the percussive sound as your right hand makes contact with the top of the guitar.