What size lumber do you need to cut? A 10-inch compound miter saw can only cut through boards up to 10 inches wide. If you need to handle wider boards, you can either upgrade to a 12-inch saw or choose a sliding miter saw. Chris Marshall of Woodworker's Journal says a 10-inch sliding miter saw "can crosscut a 2×12 or a 4×4 in a single pass," and it can make mitered and beveled cuts on 8-inch boards an inch thick or even thicker. A 12-inch sliding miter saw can handle even bigger lumber, but it's also heavier and harder to transport, not to mention more expensive.
Do you need a dual bevel? All compound miter saw can rotate to the left and right to make mitered cuts. However, for beveled cuts, some saws can only tilt the head in one direction, while others can go either way. Andy Beasley, writing for the Journal of Light Construction, says that a single-bevel saw is "lighter, cheaper, and simpler than its flip-flopping cousin," but it can be difficult to position the board correctly to make compound cuts.
Where will you use the saw? If you plan to set up the saw in your home workshop and never move it, portability isn't crucial. However, if you'll ever need to move the saw to another site, it should be easy to carry. Look for a saw head that locks in place and a stout handle – or better yet, a pair of them – on top of the saw. Also, invest in a sturdy portable stand for working outside your shop.
How much precision do you need? For most of the saws covered in our report, reviewers – both professional woodworkers and homeowners – say the blade that comes with the saw is adequate for making rough cuts, but for precision work, you should upgrade to a high-quality carbide blade with 60 to 80 teeth per inch (TPI). According to the saw blade guide at Rockler Woodworking and Hardware, blades with extra teeth make smoother cuts, but are also slower. In his test of 10-inch sliding miter saws, Marshall replaced the factory blade on each saw with a new 80-TPI Freud Thin Kerf Ultimate Cut-off Blade (Est. $65).
When using your compound miter saw, safety should be your number one concern. The editors of Fine Woodworking recommend wearing safety glasses and hearing protection when operating any miter saw, regardless of size or style. It's also important to keep both hands well clear of the spinning blade. Clamp your wood securely against the fence when cutting, and don't reach into the cutting area until the blade has come to a full stop. When using a sliding miter saw, the safest way to work is to start your cut on the side closest to you and then push the blade forward through the wood.
Reviewers – both professional woodworkers and homeowners – observe that not all compound miter saws are set correctly when first unpacked. Plan to spend some time double-checking the alignment and adjusting it for dead-on accuracy.