Tongue-and-groove boards are notorious for shrinking and expanding with changes in temperature and humidity. Unfinished boards installed in humid summer conditions can be an ugly mess during the dryness of winter. As the wood dries and shrinks, unfinished stripes will appear where the tongues withdraw from the grooves. But if you apply finish before installation, the tongues will be completely finished—no unfinished stripes to appear later!
If you're installing T&G over drywall (or plaster especially), it's a good idea to install 1x2 battens and fasten them directly to the framing with 2-1/2-in. screws. They'll give you a much more solid nailing surface. If you try to nail through the T&G and the drywall, you can't be sure the nail will penetrate far enough to securely hold. Also, the battens will somewhat flatten out uneven ceilings. Another plus: You can run the battens either parallel or perpendicular to the ceiling framing, depending on which way you want the T&G to run.
Recut the ends of every board. You'll remove staples left over from shipping wrap, cut away any splits and get clean, square edges. One of the best tricks to get a professional-looking installation is to add a 45-degree bevel, called a "chamfer." This technique is called "V-grooving." The V-groove will mask small inconsistencies in butt joints. You can either apply finish to the raw wood on each chamfer before nailing up each board or touch up the entire ceiling after it's finished.
Always plan your work so the tongues point toward the direction of installation. One of the cool things about T&G is that you can use a technique called "blind-nailing." If you do it properly, you won't have any nail heads showing or holes to fill. Drive the nails through the shoulder of the tongues into the framing at about a 45-degree angle. The next grooved edge will hide the nail holes. A 15- or 16-gauge brad nailer with 2-in. nails is the best choice for fastening, although an 18-gauge nailer will do the job too.
Installing T&G can be a real workout. Think about it: (1) You're usually working over your head. (2) You have to seat the tongues and grooves together, and they don't always want to marry. (3) T&G isn't always flat, so you have to force the boards together to get them seated. The best way to do that is also the fastest way: Use the side of the nailer to tap (and sometimes pound) the boards together. If you start crushing the tongue too badly to get the next board seated, grab a short chunk of waste to use as a sacrificial board. Don't beat yourself up trying to preserve a pristine tongue—it gets buried in the joint anyway.
There's no reason to try to join butt joints directly over framing members. They can fall anywhere because the tongue-and-groove joints support one another. Plus, if you cut the boards so they fall directly over framing, you'll waste a lot of material. Instead, choose lengths so the joints look as random as possible.
It’s really tricky to accurately mark cutouts for electrical boxes and other ceiling openings on T&G. The secret is to scribe and/or mark as much as possible in place on the ceiling rather than to try to measure everything perfectly. After you draw the opening, make the cut with a jigsaw and test-fit the board. If it doesn’t fit, you can tweak the cut. But if you really blew it, don’t sweat it. Just cut out the bad spot, use the parts elsewhere and take another swing at it. You’ll be wasting only a few inches of material.
On any installation, you’ll have times when you can’t fit the groove in the previous tongue and seat the board. In fact, it’s almost always the case with the very last board. But it can also happen at ceiling protrusions or even at projecting inside corners.
The only option is to eliminate the back of the groove so you can lift the board directly into place without locking the joint together. The easiest way to do this is to break off the flange with a few hammer raps. These pieces can’t be blindnailed—you’ll have to face-nail them and fill a few nail heads.