Installing crown molding can be a daunting task if you haven't done it before or at least done some research ahead of time. Knowing how to approach the installation and what steps to take is half the battle.
Once you have your crown molding idea laid out, it's time to start planning. Make sure you have measured correctly first and foremost. Crown molding is sold in 8' and 12' lengths so plan accordingly. 8' lengths are obviously much easier to work with but you may have seams in a few spots depending on the size of your room. Try to grab a helper if you have never installed crown molding. It can be done alone, but get one under your belt first.
With your planning complete it's time to begin. Start from the most conspicuous corner and work out from there. Try to get your seams to land in a spot in the room that is as much "hidden" as possible (this way if your seam isn't perfect it won't be as noticable). When it does come to time to seam together, always use wood glue or else your seam will crack open within a year of completion without a doubt! If you don't have a pneumatic compressor and nail gun, you'll have to go the old fashion way but I don't recommend it. Rent one if you have to.
Once you get the crown installed, it's time to caulk in all the spots touching the walls. Get a good caulk, not a low grade 10 year brand. These tend to shrink and crack easier that a better caulk. I would recommend a 40 year rating. Once the caulking is complete, pick up some wood filler and fill all your nail holes. After the filler has dried, give it a light sand and your ready to paint.
It's easiest to paint the crown first and then work the walls. This way you don't have to worry about being perfect on the crown, just on the walls.