I found what looks like a good raised vegetable garden soil mixture: 1/3 top soil, 1/3 compost manure, and 1/3 peat moss. Should I go by weight or volume?
A good recipe will tell you whether the author means weight or volume...
In this case I'd assume volume, since topsoil is so much heavier than peat moss: if you mix equal weights, you'll have way too much peat moss.
Also, note that peat moss can be acidic. I'd recommend performing a pH test on both your topsoil and peat moss. If they are acidic, add lime as your building the beds to bring pH up to around 6-6.5 (assuming the raised beds are for a "typical" mix of vegetables; other plantings may have very different needs).