Headset, craft foam, glue.
Try to raid the clearance bin or your local thrift store for a pair of white headset that sits comfortably on your head. Remove the wire if it's not wireless. It's a whole lot easier than attempting to make your own and will look realistic, especially the mouthpiece, since it's real.
Cut out the headphone pieces on craft foam and glue together. You can try using bike decals or colored reflective tape to give them extra glitzy power. Glue the headphone parts onto your headset and touch up areas with paint if necessary.
Attached image is the finished product, but it wasn't made by me.
2007 | Haruhi - The Melancholy of Haruhi Suzumiya | Shiori - Kanon
2008 | Konata - Lucky Star | Haruhi - Ouran High School Host Club | Yuki - Vampire Knight
2009 | Ciel - Kuroshitsuji | Nagisa - CLANNAD | Remilia - Touhou | Kuniko - Shangri-La | Emi - Katawa Shoujo | Ichirin - Touhou
2010 | Haruhi - The Disappearance of Haruhi Suzumiya | Eva-Beatrice - Umineko no Naku Koro ni
2011 | Minori - Toradora! | Chen - Touhou | Recette - Recettear | Menma - AnoHana
2012 | Nadeko - Nisemonogatari