Watch the The I-IV online guitar lesson by Ravi from Guitar Lab: 30 Rock & Pop Progressions
The I-IV progression is probably the most popular chord progression in western music. So many songs use these two major chords together. Use down and up strums to create more movement. Also, explore switching between playing the I-IV as open and barre chords (which are fingered in the same fret, making the barre form easy to remember and transpose). You can also play with tempos, and even divide the chord by playing the bass note on beat 1 and 3 and the rest of the chord on beats 2 and 4. It's not always about perfectly copying the original, but sometimes just capturing the overall feel and making the song your own.
Examples: You Can't Always Get What You Want, I've Been Working on the Railroad, Amazing Grace, Ain't Too Proud to Beg, Domino, Angels of Harlem, Lady Madonna, Should I Stay or Should I Go, Feeling Alright, I Can't Get No Satisfaction, Start Me Up