Making shapes in wood is what got me into furniture making. I recall seeing the sculptural curves in Sam Maloofs work and coveting his job. Don't worry, I won't be drawing any comparisons between what we do except to say that there is a lesson that I drew from looking at his results, and the results present in so many Windsors.
The basic idea is simple, each shape should have a geometric logic within itself and a sense of tension with the other pieces that it joins to. Without this, parts and entire pieces of furniture look "ooey gooey", like they are melting or have worn slack.
I have a few techniques that I use to help create the logic within a piece. Mostly, they involve following a series of geometric shapes as inbetween steps so that the final shape has a hidden framework that helps define it.
I was thinking about this today while shaping the curved stretchers for a rocker that I am finishing. I had some issues when bending the stretchers turned to their final shape, the tapers had too much runout and cracked. So I turned the piece at a cylinder and bent it. The bend went fine, but then it was up to me to carve the tapers.