Well, zoom in is normally my second step in using pen tool. The first step is controlling the ctrl and alt by clicking at the path point. Shift is also a very useful button in controlling the path. After you got the shape you wanted roughly, there's always tiny curves that you've done unwell which you cant see under 100% screen. Thus, this is the time when you need zoom in. You zoom in and redrag the points, control them and make the tiny curves became flawless. IT shall turn out a smooth curves with any shapes you like. Good luck.

Yea, bem69 is right. In using pen tool, u have to keep on practising until u get the best way. I practiced alot too.