I couldn’t let GUGUG week go by without some reference to the Ramones (although this song was originally done by the Rivieras).
The chords for it are dead simple and so is the strumming. For most of the chords you can do a down, down, up, up, down. The only exception are the F and G chords on the, “…warm California sun” bit. For each of those do a down, down, up.
The tricky bit is the little riff at the end of each line of the verse.