Start Phase
The fastest athletes often times have the quickest starts, you can see this when watching live coverage of the NFL combine/pro day. With that, the most important part of the start is the set up. When getting into the three point stance, it is critical the back foot does not start too far behind the starting line. There should be a nice forward lean into the front leg in order to shift most of the weight off of the rear foot.
The first movement should be a drop of the front knee while the hips roll forward and the back arm comes firing forward and through. The rolling of the hips is similar to a broad jump or power clean in order to maximize explosive horizontal force. While I do not love the queue to stay low during the start because the spine must rise to get the hips through, it is important to keep the chin tucked and eyes down to prevent yourself from popping up.