Find your source material. Your source material, in the case of a found poem, is any text not intentionally poetic. Magazines, newspapers, blog entries, food ingredient lists, wine bottle labels, employee handbooks and advertisements can all be used and dissected to create the building blocks of your found poem.
Extract phrases and sentences you like or that speak to you from your source material, and compile the text on a blank notebook page or in a new word processing document. You can attribute each quotation if you wish, but it's not necessary for a found poem.
Arrange the phrases and sentences you like by theme or common characteristic. Some of the phrases may mention color, some sentences might deal with physical sensations; group them according to common traits you identify, and copy and paste your found items accordingly.
Write your poem. Take a group of found phrases and sentences that you particularly like. Use them to construct a narrative. Don't worry about making the narrative poetic yet; just get your thoughts onto paper, and edit to make it more poetic later. Include your own words and phrases where you need to link separate ideas or images.
Try telling several different stories using the same group of found text. This will exercise your poetic muscle and get your brain working hard to find inspiration instead of waiting for the poetic muse to come to you.
Revise, revise, revise. Treat your found poem a work in progress. Revisit them after a day or two to see if you can clarify certain ideas or images, either by inserting additional found material or using your own words. Play with the structure, repetition and enjambment of your found poem to make it as poetic as possible. Ask others (your peers, a professor or a person whose writing you admire) to read your found poem and give you feedback.