If you're renting, or you just want to avoid holes in the wall, you probably don't want to use thumb tacks to hang posters. Fortunately, you can use a thin layer of toothpaste to hold posters in place.
Photo by Jose Taco Cruz.
You'll want to make sure that the toothpaste doesn't have any whitening chemicals or breath-freshening additives. Regular toothpaste can make a nice, light adhesive that won't leave residue on your walls. When you're ready to take the posters down, just pull them off, give the wall a quick wipe, and you're done.
Hang Posters With Toothpaste & Shampoo [Apartment Therapy]