Since I just started reloading about 6 months ago, I can tell you what worked for me. I asked these forums (and others) what the best loads the members had for my combination of barrel and intended use. Then I started low and worked up watching for pressure signs. I did it in three cartridge sequences. I watched the groups shrink with every grain toward what people had told was their best load. Then when I got to the full load, I went back and judged the groups to see what worked in my barrel. I also found out a great deal about my gun (like how the trigger pull affects group size) I did not know. Most of these guys will let you know generally what certain caliber barrels and lengths prefer, as far as, bullet type/weight. The same with powders. Then I settle on a powder/primer/bullet weight that I can readily get and work from there.
By the way, after shooting one powder and not getting great results, I switched to another primer and then to another powder. You have to reduce the max load, of course, and work up. But, that is the fun in reloading for me.
ps Use the search engine and you can find every post on certain calibers and a lot of times find existing loads that have already been shared.
