Get them framed
It costs a bit of extra money, and it's a bit of a hassle, but I think it's entirely worth it to get your posters framed. This goes double if they're posters you particularly like, so that they last longer without fading and so you don't cause any damage with nails or tape.
Framing a poster takes a room from college dorm to adult living space in an instant. There are also many places you can buy frames for particularly cheap, like Ikea or Amazon, and they do the job just fine. If you're trying to decorate your space, framing your posters give a level of polish that just can't be achieve with blu-tac and paper.
Double-sided tape
One of the easiest ways to hang up your posters and ensure that they stay up is double-sided tape. There a variety of sizes available from different brands at most grocery stores. Double-sided tape will keep the front part of your poster intact even if you have to readjust it. The tape stays out of sight for sleek look on your wall. While it will keep your poster up, it's not extremely heavy duty. This means there will be minimal damage to your walls.
