ballistic

I'm riding a 2010 Fuji Roubaix ACR 2.0 with Shimano R-500 wheels. I really want the Park Tool TM-1, but it's just under $60. I don't have any way to measure my spokes' tension, but what's a good resource for finding out what tension they should have? I've Googled and found some seemingly random PDFs and such, but I'd like to know if there's a better source first.

Also, I know I can tune my spokes by sound, but there's still the matter of knowing the right note.

Thanks!