Watch this video from This Old House to learn how to make miters.
1. Use traditional wooden miter box and backsaw for making simple 45- and 90-degree miter cuts.
2. Lay molding in box and hold it tight against back fence.
3. Set saw in appropriate slots, and make cut with slow, smooth strokes.
4. To hand-cut a wider range of miters, use an adjustable miter box with backsaw.
5. Rotate the saw to the desired angle, lock the saw in place, then make the cut.
6. When extreme precision isn't required, you can cut 45-degree miters using a portable circular saw and speed square.
7. Hold the square against the board, then guide the saw along the square to make the cut.
8. For the optimum miter-cutting accuracy and ease, use a compound-angle power miter saw.
9. Rotate the saw blade to the right or left for making straight miter cuts.
10. Tilt the blade for making bevel cuts; note that some saws only tilt to the left, but dual-bevel models tilt both left and right.
11. Set the miter angle and bevel angle at the same time for making compound-angle cuts, such as those necessary when installing crown molding.