Search the internet for an image of your favorite food, toy, sports team, Logo etc.

Try to match the font with a font on your computer or use an existing letter from the product and alter it (like the snickers practice) and change the name of the product to be a funny name.

Crop the original, alter it and place it on a 5"x 5" canvas. Give it an interesting background.

Include a slogan that is found with the original ad/product and then change it so it relates to your spoofed ad.