Generally, you find the length of your arrow first. I usually go 1/2" past the rest (this is shorter than your draw length). Use this length to enter the charts under your bows draw weight to get the spine for your arrow. Weight of the tip will also come into play in the equation.
That look on my face is not concern, its shock at your utter stupidity!
Check out Redneckarcher.com. It's an adult archer/hunting site that feels like hunt camp.