For perfectly perfect points...paper piece.
Past that I find it is ALL in the pinning. When I am doing points that I really, really want to come out right I use the Clover fine Patchwork pins (they come as half yellow headed pins, half blue headed pins), which are so fine you can sew over them.
If I am in doubt about my seam allowances being entirely trustworthy, I put a pin through the point and the opposing fabric, which keeps the layers in place before I pin on either side of it.
Extra insurance: BASTE. Baste the seam with a long, easily removed stitch. That way you can see if you are getting your point sharp before committing to the tighter stitch width. That basting step shows you where you might be off and making adjustments are easy after that.
In some projects you just have to have those crisp, sharp points. Just takes time and practice.