Today I have mostly been sewing darts using a method i've seen in various places on the interweb. It works a treat!
First of all mark the bottom of your dart with a little cut on each leg.
Then fold the dart, aligning the two cuts.
On your sewing machine, make sure your top thread (the one that goes through the needle) is quite long. Place the piece under your presserfoot and sew one or two stitches. Then lift the presserfoot while the needle is still down, and bring that top thread forward.
Pin the thread to the end of your dart so that it creates a perfectly straight line of thread which marks the line for you to sew along. Sew along the line and taper off at the end in the usual way.
et Voila! A perfect dart.