I have always been very soft-spoken. Recently I've made an effort to speak more loudly when I first meet someone, almost to the point where I feel ridiculous, and I've noticed that I get a LOT more IOI's this way, some of them rather intense.

Still working on the rest of my game, but just a reminder--a loud voice is perceived as both dominant and vulnerable--it's an easy adjustment that can make a big difference to attraction.