When I'm working away with the pen tool in Illustrator, I always click on an (curve)anchor point after I've made it. This gives it one control arm instead of two, and allows it to control the curvature of one segment, rather than both segments on either side. What I haven't figured out, is how to do this to an anchor point that is added to the path after I am done with the shape. Y'know what I mean? It always wants to have two control arms and effect both segments.
hit (a) this is the direct selection tool (the white arrow tool). in order to get only 1 curve controller just click on the actual line. in order to get both curve controllers click on the anchor point, you can then move the controllers individually