#1 - Gun stores are a good place to go for advice on firearms and shooting. This isn't to say I haven't heard good advice in a gun store. On occasion I have heard or been given excellent advice. I've also heard some of the most cockeyed bad advice I've ever come across. Seek advice from several sources!
#2 - That I could shoot well. This one seems to be a failing of people possessing the XY chromosome pair every where. Didn't take long after I joined a club to be exposed to fellas who really could shoot well. I began to improve after that.
#4 - Cartridges should be loaded to near or max charges to be effective. There are some situations where max loads are called for, but by and large more moderate loads are easier to shoot, easier on the gun and the brass, and will usually get the job done.