I read once that an artist kept a folder of photos in his studio. In the morning he would just put his hand in the envelope and whatever photo he pulled out would be what he used for his warm up that morning. I liked this idea and I have tons of photos that I have taken using my digital camera. When I paint outdoors I would usually take a few pictures so that I could have reference to finish the painting at home if I wanted to. I also would take pictures of whatever I found interesting that I may add to the painting.
Passers by would of course wind up being photographed and sometimes I would use these photos to warm up. That is the case with these sketches from my sketchbook where I took 5 different photos as reference.
I have also been working on Video tutorials using Sketchbook Pro 6. The video bellow is from my YouTube Channel.