You need to buy ten manuals, and 30 powders...
Only half joking...
My favorite light-magnum plinking load for the 158gr bullet is 5 grains of Red Dot powder with a standard primer...
My favorite medium-full magnum load under 158gr jacketed is 15 grains of H110/W296...
Every gun/load combination is a world unto itself, and what works in mine for me, may (or may not) work for you in your guns...
Research loads online, gather all the manuals you can, read how to load and what small differences in components make, and you will be well on your way to safely (and accurately) enjoying your guns...
Hodgdon site for data:
http://data.hodgdon.com/main_menu.asp
Alliant 2004 Paper Manual in PDF format (.357 mag info on page 42):
glarp.atk.com/2004/2004Catalogs/2004AlliantPowderSM.pdf