Ok. Here is some information to get you started:
Hmm, he could say the color of the hat on the guy in front of him. That guy would then guess correctly, but then the next guy would be in the same situation as the first guy. Repeating this idea gets only 50 prisoners out guaranteed, with an average of 75 getting out.
But, we can do better. We can actually get the rest of the 99 in line to get ti right.
Please note the answer does not involve any tricks of signaling the answer by touching, or pausing. It only relies on each person guessing black or white.