The bend is usually pretty easy. What you want to see, which is to say, what makes a pipe look pretty, is smooth, graceful curves. This can be achieved with constant-radius curves or with exanding/contracting curves (french curves) but basically one smooth line is what a guy wants to see.
The stem length on certain shapes is set by tradition and by mathematical relations occassionally, but on a freehand it's much more difficult to decide. I generally look at whether I am trying to build a churchwarden, a regular sort of shape (cracking in around 5-6" total) or something in between. The big question I try to answer is "Is this pipe going to be comfortable."
So once you've set your curves and established a bit of a taper, the stem will just terminate as the two curves come together (in a perfect world).
So like I say, it's real easy.
![Laughing :lol:](./images/smilies/icon_lol.gif)