The warm salt water only works when you're at the beginning of a sore throat--the salt is supposed to make an environment in your throat that is unhealthy for the bacteria that infect your throat to breed. So, by the time you have a full-on sore throat, those little bacteria are everywhere. I had a Bio teacher in HS who would gargle with hot salty water every night to prevent getting a sore throat.
I totally agree with Hootie. Vitamin C! Vitamin C!