Contextualize, Anthropomorphize and 'Narralize'. This is a scheme that seems to me to be an effective tool for the process of creating humor. I've never heard it in this particular form before, because I've made it up. But you can probably see how it is been widely used. This is how it works.
(1) Pick a subject, preferably one you're already familiar with, and think of its regular context. Think about its most important qualities, its function in daily life, the most common phrases we use for describing it, well-known situations and problems surrounding it. You can write down and highlight some of the things you think are most fun or interesting. Keep it simple and specific.
(2) Anthropomorphize the subject. This means you've got to give it human feelings and qualities and/or make it behave like you or any other regular human being does. An easy way to do this is to ask the question: 'What would it be like to be an X?' You might already have thought of some funny ideas at this point.
(3) Now you can think of a narrative that combines the pieces of information. What would it be like to be an X and be involved in a story of ..? This line of thinking will probably lead to more abnormal situations and therefore (potentially) to more funny situations or jokes.