|Have you ever had the problem where your darts look pointy on the end, causing an unflattering point right over your chest (or butt, depending on what you're darting)? It's probably because your seam isn't perfectly straight. Many peoplehave the tendency to sort of "curve" off the edge of the fabric too soon.
To combat that problem, mark along your dart seam line with masking tape and sew from the outside of the garment to the point of the dart RIGHT ALONG THE TAPE. Do not deviate. Leave yourself enough thread at the end to tie a knot. Do so and remove the tape - you should have a perfectly shaped dart.
This method works for any spot where you need a crisp point and you can use low-tack painters tape for more delicate fabrics.