I just finished doing crown molding in one room. My thoughts as I finished were that the reason they put the ceiling so high up is so that you wouldn't be able to see how bad the crown molding joints were.
No matter how perfect your cuts are, they'll still be off.
OK, that out of the way, unless you have a compound mitre saw, you're going to have a very difficult time of it. Set the mitre at 31.5° and the bevel at (I think) 33.5°. This assumes you have 90° corners.
If your saw does not do compound mitres, you can set the mitre at 45° and rest the molding against the fence at an angle (the angle at which it will rest against the wall.) You'll have to cut the molding upside down (ie ceiling-side resting on the saw base, wall-side resting against the fence.) It's a good idea to mark on the fence where the molding is resting, (draw a line along the molding as it rests against the fence) so that you cut all of the pieces with the same attitude.
When you're done, fill in the gaps (and there will be gaps) with caulk, wood filler or even plaster.
Some people will tell you to cope the inside corners and mitre the outside corners. I find coping to be even harder than mitring.
*Another good trick is to cut the mitres on very short pieces (about a foot long - or whatever you can work with best) and assemble them with glue and finishing nails on the ground. You'll get perfect, right-angle corners. Then, put the assembled corners up on the wall. You can then splice in the straight pieces of molding along the walls (either a straight 90° splice or a mitred splice.) It makes the process a little less unwieldy.