Most strumming is simply moving your right hand up and down over the strings. Notice how at one point in this example the right hand moves up and deliberately misses the strings to keep the pattern going. There are many different patterns you can use and often you will play a suitable rhythm without giving it much thought as strumming is a very natural part of your playing.

Funkier types of rhythms are created by having the strumming rhythm as 16th notes and then relaxing the left hand to produce ghost notes where appropriate.

Example 2a