Watch the Syncopation online guitar lesson by Jason Loughlin from Country Guitar Survival Guide: Rhythm
Here's a very easy way to think about syncopation. It's putting stress on rhythms that are normally not accented. For instance, in 4/4 time the pulse is on beats 1,2,3 and 4. Depending on what kind of music you're playing your 2 and 4 can be stronger or your 1 and 3 but the pulse still remains on 1,2,3 and 4. By accenting any rhythm other than those beats you will create a syncopated feel.