A bench pin is one of the most custom tools in a metalsmith's toolbox. They start as an ordinary piece of wood and become a tool as individual as the artist themselves.
I've seen many different forms and ways of modifying them. the one from the Flickr image is an old one of mine (I swap them out every few years as they become too mangled for me to be happy with them just as a personal preference)How to start? simply saw into your bench pin- (I'd go about an inch deep) if you think a notch will help you make a notch....don't be afraid to change it around to something that looks different than everyone else's...we all are individuals, and work in many diverse ways.
here's a a pic I took of a bench pin at a well known jeweler's shop I visited last summer....it was the first time I saw pegs attached to a pin, so I had to get a pic...
see? pretty different, but perfect for what he was doing...and quite a cool piece of sculpture too if you ask me :-)
one thing that is helpful as you sit at a bench pin is your positioning- I recommend to have the shoulder of your dominant hand (right for me) lined up with the bench pin--just shift your chair to the left slightly instead of having the bench pin straight on-- this simple adjustment in your positioning seems to help many 'smiths-beginners and more seasoned metalsmiths alike.
(this image is also the avatar for my Facebook Metalsmithing group called "Metalsmiths Unite!" it's an informal, friendly, non-competitive community of metalsmiths...come and join us if you are looking for a group of friendly 'smiths!)
So- My advice to newbie smiths is to dig in and have fun...and don't be afraid to get your bench pin a little messy :-)
happy 'smithing!- MBZ