I wanted to elaborate a little more on some of my mountain biking tips since I realize just because I know what I mean, you may not! Just two small little comments.
When I say to lean back on the downhill, you should get in a tuck position. If you look at the photo of me on the right (the action one), you can see I am ducked down on the handlebar, my face is kind of close to the bar, and I’m leaning my butt back. When I say shift your weight back, push your butt back. Another tip for downhilling– keep your knees bent. Don’t lock them up so they can absorb more shock. Also, if you are going over rock, use your arms. push down. It helps your shock rebound at the right time and gives you more control.
Another quick tip. If you’re riding through a rocky section and you lose your momentum, but you can’t pedal because the rocks are too high, backpedal about 1/4 of a revolution, then pedal forward. It doesn’t give you much speed, but it will help you not completely lose it.