There's a lot of good information out there from bike setup to technique reminders. This is where to find what I find useful.
Bike Setup: Brake Levers
Fluidride has this succinct video and advice about where to place you brakes for optimal control. I've earned a Fluidride teaching certification so I'm a big fan of his perspective.
Riding within yourself
Riding in a relaxed yet alert manner can reap dividends on unfamiliar trails as Simon of Fluidride discusses here. It's also a good approach on familiar trails which can change due to weather, maintenance work or even the rider ahead of you.