I go through as many manuals as available and note the common "most accurate load" listed. If two or three manuals list the same powder that is a good one to start with. I also look for top velocity and close to a 100% fill level. If this also has lower pressure then it is a good choice. I will also pick the temperature tolerant powders first. Then I consider things like good metering, clean burning and availability. A good place to start is with JBs "Loads that work" old and new and "Pet Loads" by Ken Waters. Each of these writers have extensive experience and will up any ones learning curve on reloading.

"When you disarm the people, you commence to offend them and show that you distrust them either through cowardice or lack of confidence, and both of these opinions generate hatred." Niccolo Machiavelli