Start collecting photos and postcards that interest you. Look at the photos carefully and write your own original captions for the photos. Think of the photos as one-panel cartoons, and make your caption tell a complete story. It's harder than it sounds. Try turning the photos upside-down and sideways — remember, you want to look at things differently — and see the photos as you see them, not how everyone else would see them. Paste the photos with your caption into your notebook. Can you write a sketch based upon your captions? Can the photo be used as a starting point for a sketch?
Now, start looking at life that way. Take the time to just stop and watch the world. Watch ordinary people doing ordinary things and question what you see, and pretty soon you'll start seeing your own comedy vision.