Any SF Bay Area mountain bikers? Looking for info.

Hey all. I just bought my first mountain bike. I don't know much about mountain biking but when I've taken a hybrid out onto logging trails it's been super fun so I'm sure I'll enjoy it. I have a few questions before I head out into the mountains:

1. What kind of mountain-biking specific gear do I need?
2. Where should I go as a beginner? Ideally somewhere with not too many hikers or other cyclists. I have plenty of stamina from my regular uphill cycling routine, but I don't want to get into intense steep riding and jumps right now.