First, think of all the things that could go wrong reloading a round. Then, don't do those things!
Make sure yer primers are seated, there's only one powder charge per cartridge, and the finished cartridge will chamber and you'll be fine. But I remember my first reloaded round; .38 Special. I held the gun at arm's length, turned my head and covered my face with my hat and squeezed of Round Numero Uno! That was in 1969 and I've been enjoying reloading since (sometimes I get the ???s when I reload a new round, but never had a major problem).