Depends if you're wanting to stay in Haad Rin (where the most popular beach is and the main party) or somewhere like Ben Tai (half way between the port and Haad Rin, and close to the build up parties). The better hostels seem to be near Ben Tai, or at least that's the vibe I got. I'd personally stay away from the Hard Road chain of places as they're over rated; most hostels seem to offer the same stuff but my personal favourite was Ringside! Lots of common areas so easy to meet people. Also book as far in advance as possible or else the prices rise quickly closer to the time.