Buy some manuals...
I was talking to a soon to be reloader, I said you gotta be patient and see what your gun likes..I got a deer in the headlight look...He saked "if you load your ammo with the same bullet and powder charge why wouldn`t your gun shoot them all the same" I said all guns are different and like different loads. Again he asked "but if everythings the same why wouldn`t they be accurate" ? I kinda got stumped and said thats just the way it is...Someone help me out here
Buy some manuals; pick 1 load. buy the components and make up enough loads to qualify the results; If you like the results, keep that recipe. If not, pick another load. Load a number of shells, shoot em up and take notes again. If you see improvements keep improving. If not, go back to square one. It depends on the amount of perfection you require.
Nothin is finite when choosiing a load because of all the variables. The only specific is that you keep it safe and as simple as posssible. Change one component characteristic at a time. ie charge weight. or bullet weight or case brand, etc. Multiple changes confuse your findings because if there is a change in performance you will not know what change made the difference.
The comment that everyone is an expert in his/her own mind may be true, but even a qualified expert will probably say...it is all easy, but it still takes experimentation to find your best load. And then after all that, the weather may change.