I know I'm probably the meanest dog owner ever, but when I decided we'd do a little birthday celebration for our dog, Milou , I knew I had to make him his very own birthday hat.
I gathered supplies at The I.D.E.A. Store , including some red polka-dotted wrapping paper (I was looking for heavier scrapbook paper, but didn't see anything I liked, so I figured I'd make the wrapping paper work) and some pom-poms that looked like they used to be strung together on pom-pom trim.
I decided to cut apart a brown paper bag and use it to experiment on making a hat shape. I thought I could figure out how to do it on my own, thinking I'd measure the dog's head, calculate the circumference and go from there.
I should know better than not consulting Google before starting such a project, because it got frustrating. I then found this easy-peasy tutorial  that helped me figure out how to make the cone shape by measuring three points and cutting a curved line between them.
I measured 10 inches, but in retrospect, I thought the hat was a little tall (and wizard-like) for the dog. I'm guessing it wouldn't be too tall if you were making it for a human, but I don't know for sure.
I cut out the shape on brown paper, and the decided that it looked decent enough that I could just use it as an underlayer for my wrapping paper.
I laid the paper-bag cutout over the wrapping paper, cut the wrapping paper about an inch bigger on each side, and used Elmer's glue to attach them. I folded the wrapping paper around the sides carefully, so it looked neat and even.T
After it tried, I rolled the paper into a cone shape and secured it with hot glue.
To cover the seam, I glued white pom-poms up the back, and then around the bottom as trim. I then added a pom-pom to the top and told myself I could use the hat again when I take Milou to be photographed with Santa.  (Just kidding, that would be too much for our poor dog.)
I measured Milou from his ear to below his jaw and cut two lengths of ribbon for tying the hat on. In retrospect, elastic might have worked better, but we didn't have any and he has a bad jaw, anyhow.
He allowed us to put the hat on his head as long as he was getting plenty of treats (or doggie cupcakes ), and I think it came out pretty cute.