I wanted to ask anyone that has been in a YC batch: What are the resources that PG recommends regarding sales/marketing and gaining initial traction?

I imagine that many talented, ambitious engineers and entrepreneurs on HN follow the lean method, but still frequently end up with a solid product that they need help growing. Technology doesn't sell itself, and sales can be extremely difficult for engineers. So what advice/resources does PG provide to help technical YC founders land big customers early and start out strong?