Off-camber corners are the same as a regular corner, except you have less grip to spend on speed. You take them slower than the same flat corner and be extra careful with the throttle-cutch and brake control.
Your lean angle - since the ground is already angled away, you can't lean as much as on flat ground.
Cornering on a berm is much faster than a flat corner. The centripetal forces acting on the bike will actually push it more into the berm, increasing traction. Thus, you have more grip that you can spend on speed or later braking or harder acceleration.
Ruts are similar to berms, with the exception of... making it into the rut. It's better to enter more slowly and get both wheels into the rut, after which you can go similar to a berm.
While taking any kind of corner, it is important to weight the outside peg, as opposed to the inside peg or the seat. The more weight on the outside peg, the lower the centre of gravity and the better the traction.
Here is an article with more details on weighting the outside peg.
This is a great video on cornering on a mountain bike - pretty much everything is directly applicable to dirt bikes: www.pinkbike.com/news/Fabien-Barels-videos--how-to-cornering.html.
In fact, practice leaning on a mountain bike is also pretty much directly transferable to dirt bikes and allows you to practice a lot closer to home (even the driveway) without hauling your bike for hours...