If you are doing this as a lark, pick another project as this one can potentially drive you absolutely batty and leave you awfully frustrated. On the other hand, nothing adds a nice touch to a room like crown molding ...

If you got this far and insist on proceeding, get ahold of the May 1990 Family Handyman, it has a good article on the ins and outs of crown molding. It is available through FH backorder services.

NOTE: Remaining tips assume you've read article from tip #2:

Unless your house is newer (mine is about 70 years old), don't plan on being able to reliably find studs or joists. The only thing you can count on is the wall header. Even with a good electronic stud finder, my walls had all kinds of two and three layer drywall sections that threw the readings off. Plan on using the canting block method all the way around.

No matter how square and plumb the walls and ceiling look, they are not even close. Just resign yourself to the fact that it's a minor miracle if they are.

Unless you're really, really good at this stuff, plan your decor so that you can paint your crown moldings instead of staining. Spackling works wonders. See tip #4.

Buy one pint of spackling for every 100 feet or 50 years of age (the house, not you). Do some finger exercises one week prior to actually spackling or check your workers comp plan to see if there is coverage for "spackling finger". The problem is not so much poor fit which needs to be spackled, but that since crown molding only touches the wall and ceiling at one spot each when you spackle it literally "disappears" behind the molding unless you put on a few very light coats (which is recommended of course, but not always followed).

Paint the walls, ceiling and molding prior to installing the molding. This way you don't have to worry about the wall/ceiling line being painted accurately. You'll have to repaint or touch up later, but you might as well get one good coat on so that the painting after assembly goes quicker.

NOTE: I used standard 52/38 degree molding with a 2-7/8" rise over run. As well, my molding came to a "point" at the bottom edge, which meant the coped section was VERY thin at this point. If I did it over, I would select molding with more substance at the bottom edge so that the coped section would not be so thin.

To make the canting blocks, rip a six inch section of a 2x3 stud at a 45 degree angle from one edge. Then rip the other side so that from an end view about 3/4" of the result is rectangular and then the 45 degree angle slopes to the edge. Then cut the result into two 3" long blocks. Cutting a completely triangular canting block from a 2 x 3 ended up too far from the molding for comfortable nailing. The scraps make nifty "keepers" for other projects.

  Ceiling side        Crown
   _____________       ___
  |             |     |   |
W |             |     /   /
a | Canting     /    /   /
l |  Block     /    /   /
l |           /    /   /
  |          /    /   /
  |         /    /   /
  |________/    /   /

Note that the molding stays 1/2"+ away from the block. You probably don't want it touching the block as that may throw off alignment.

Nail the canting blocks into the wall header about every 12" along the wall/ceiling line with 6d finish nails. The article in tip #2 calls for 10d or 16d or some such thing. Unless you want to watch plaster crack, use the 6d's. Don't worry, the molding ain't comin' down anytime soon. Make sure you start about 3-4" in (or closer) from each wall edge. The article in tip #2 states if you're coping you don't need support of the mating piece in the last 18" -- baloney. The wall/wall/ceiling meeting point is where all the plaster builds up and chances of being square are ridiculously low -- you need all the support you can get. Remember, it is much better to put up a block you don't end up using than wishing you had a block there after you've nailed the rest of the molding in place!

Mark the position of each canting block with the guide jig detailed in article in tip #2 on the walls and ceiling. If you use a normal to wide-bodied pencil, your marks will be about 1/4" outside the edges of the crown (the picture in the article shows the marks flush to the edge). You can compensate to get marks flush to the edge (change jig or pencil) but I left them 1/4" out -- they were easier to erase afterwards. I marked the walls and ceiling just to the right of each block, that way when nailing time came I knew I had 3" to the left of each line for nailing.

Do not have your spouse help you. Pick an independent third party, never, never your spouse. Putting this stuff up is frustrating, and you probably want to take it out on a friend instead of your spouse ...

Follow the cutting sequence mentioned in the article. This is a great time to justify that compound mitre saw you've always wanted. Get one with the angle markings for crown molding so you can cut it flat, otherwise you must put together a fence set up so that you can cut it upside down.

Build yourself some sort of support for the molding during the cutting. It takes time but it'll be worth it.

Coping is relatively easy, don't be gun shy about tackling it. I did use a Dremel to "clean up" the inside of the coped edges so that the mating piece fit snugly -- it's much quicker than abrasive paper. The article in tip #2 calls for a 30 degree back cut, but my molding required more like a 70 degree back cut. Check your molding before assuming 30 degrees will do, although trial and error is the best way to find out and it won't hurt to start small and increase the angle.

"Nibble" the lengths as the article states, but don't be hugely surprised if you nibble that last 1/16" off the length and then the sucker is 1/4" short! Just watch the cussin' in front of the kids. One thing to make sure of is that you file the back edge at each end of each non-coped, non-mitered piece so that it's not a sharp angle. Where your walls meet is more than likely rounded over so you should make sure any non-coped ends of your molding are rounded over likewise. A piece that may appear to be too long might actually just need the back edges filed off in order to fit.

Per the last section of molding you install, which is most likely coped on both ends (or any other section coped on both ends):

Don't assume the overall length (bottom, pointy end of one cope to bottom, pointy end of other cope) will drive the other dimensions. For that last section, measure the top-to-top length and the bottom-to-bottom length needed, then make your cuts.

If you have to spackle, quickly follow the application of the spackle with a damp sponge. Your goal is complete coverage with no sanding necessary later. You won't hit that goal, but if you go in with that goal you'll have a lot less sanding and painting touch up later. It helps if someone can run sponges back and forth from cleaning at the sink while you're on the ladder. The angles of the wall/molding/ceiling end up being quite a pain to get leverage to do sanding, so be as neat as possible during any spackling, you'll be glad you did.

Pre-drill your nailing holes in the molding regardless of the material. The absolute last thing you want is cracked molding after putting up a 16' section.

When pre-drilling and nailing the molding to the canting blocks, pay attention to the resulting angle the nail will take. Sometimes getting leverage to use the hammer on a funny angle is impossible on one end of the molding, depending on whether you're ambidexterous when it comes to using a hammer. After the first few nails go in I'm sure you'll get the hang of it.

All-in-all, putting up crown molding is alot like preparing a 10 course meal. The cook sees all the details and grunt work and in-between (ugly) stages and by the time the meal is ready the cook has lost interest in eating -- although others will rave about the meal. Same thing here -- you'll know where the extra nails and spackling are, but chances are no one else will and they'll think you did a heck of a job ...

Good luck and happy nailing!