Well, as being a fairly new goalie.. and having that problem all of the time, here is how I solved it.

I measured my stick from the butt end 36" down the shaft and made a mark on the paddle. I lay the stick butt end against the post and mark the ice where the mark on the stick is. This gives me center of net.

I then pay the stick out and with the butt end on the center mark, pointed it at each face off dot, and down at center ice.

I make a ">" mark at each position. I then draw a line that crosses the crease line on the angle. I have done this with a marker, and with a ice pick.

To check my angle and position, all I have to do is quickly glance down. The marks tell me my position, and the lines give me an angle to center reference.

Perhaps a bit involved.. but hey.. I am an engineer ;-)