I was playing around with Photoshop CS6 and wanted to learn how to do Bokeh! So I took a random photo and made it blurry and played around with the hue/saturation and the levels.
Then, I just used the brush tool on a hard round brush.
Inside of the brushes folder in the options bar: I can change the shape dynamics and check off Scattering.
Run the brush across the picture. You can change the size of the spots to give it a more varying pattern.
Filter>Blur> Gaussian Blur to make the spots blurry.
Then you add a new layer and do all the same things but make each layer a little less blurry.
You can play around with the transparency and the normal menu on the layers panel.