Sounds like you're on the right track. You do indeed need to be up and over your handlebars, but also seated depending on the terrain. Every section has its own properties, and the only way to know what each one requires is to try it.

NurnNotice also mentioned tires, which is a big factor in traction whether standing or sitting. There's a section on a trail I recently explored that I just know I could get up if I swapped from my Black Panthers at 28 psi back to the Fire XC Pros at about 25 psi. I'm not a fast rider, so being able to stay on the bike over technical stuff is a source of pride for me.