Hi,
What do you have for manuals right now? Hopefully you've got a couple of the hardbound ones--Hornady, Lyman, Sierra, Speer and Lee among others publish them regularly--supplemented with up to the minute data from the powder companies on their websites.
From there, you're going to run into a bit of a bump in the road: a LOT of powders will work in the .308, but WHAT powder you can get a hold of right now is going to limit you in today's market. So find a load with a powder you can get, and if you can find a couple of different powders, even better!
Then work it up slowly from a "starting" load (either the one given in the book, or, if none is given, 10% less than max (by weight) and see if there's a "best" combo for you. As I'm sure you've seen said uncounted times already, each gun is a rule unto itself and what works best in "my" gun might not be the same as what "your" gun is most pleased with.
Folks have different ideas on "working" up: some use a starting load, then up it in half grain increments. Some work it up in smaller steps, like maybe every 0.2 or 0.3 grain. If I'm really serious about a load, I'll do the half grain thing, then look for the best in that range. From there I'll work up and down in increments of 0.2 gr to see if there's an even "sweeter" spot. With some recipes, there is a rather small "perfect" range for "your" gun, others are pretty forgiving and the "window" is much larger. There's only one way to find out!
Rick C