I remember I was making curved line ok a month ago. Now I can't seem to get curved lines in photoshop! ??: I know this sounds stupid, but I really forgot how to do it.

I recall I used to use the pen tool to draw curved lines, and remove the fill or something and now, when I draw a curve. The top part and end part of the curve has a line, which cannot be removed when I make fill opacity = 0. ( which was a trick which used to work ) Any ideas on how to make curved lines? Thanks.