D UDUDU
The strumming pattern above should be done with a downward motion. D is short for "down" and U is for "up". For example, D UDUDU means down, up, down, up, down, up, down.
The strumming pattern can vary depending on the song. Some songs may have a faster or slower tempo. Some songs may have a different strumming pattern altogether. However, the basic strumming pattern above is a good place to start.