Being able to get the right amount of boom vang on while you're sailing, and getting it set correctly and quickly is not only beneficial to your speed and sailing but will also allow you to get the right amount of control on when you are tired.
To summarize: use high quality lines and block, make sure your floating block goes all the way to the boom vang key when it is off all the way, set your max off knot at the right tension, use a plastic handle, and mark your vang line for 90º, block to block, depower 1 and depower 2.
