Here's how I work up a load for both my Long range varminter and my long range rifle. (some things are obvious)
1. pick a bullet weight
2. Start with quality components, Brass and Bullets
3. research all possible combo's that will get you closest to what you want.
4. weight sort all bass to 0.5gr, all bullets to 0.1gr
5. find your OAL for that bullet touching the lands
6. using a micrometer seating die choose an arbitrary seating depth some distance from the lands (0.010"- 0.025")
7. Using fully prepped brass, (trimmed, chamfered, debured flash hole and case mouth, necks check for concentric thickness) pick a primer and use just that one for now.
8. with primed cases pick a likely powder (I usually start 1-2gr below book max), charging 5 cases at a time I will increase the charge at .5 gr till I reach book max.
9. seat your bullets, all weighing the same if you can.
10.I also prefer to use concentricity gauges, Sinclair and Hornady, as the Hornady allows you to corect bullet run out.
Now it's time to go to the range and see what happens
11. now taking your results from the range, using what charge showed best accuracy, make up 5 using every different type of primer you can get your hands on and go back to the range.
12.fine tun your powder charge (if your going to increase above Book max be damned careful and check each case at the time of firing for pressure signs and stop if/when you encounter them
13. taking the results from your previous trip start playing with your seating depth. I generally adjust mine by 0.005" per group
Of course there is a whole method for finding the seating depth your rifle likes spell out on Berger's website.
(I'm kinda anal about those 2 rifles