Reading his work out loud ands starting to HEAR the patterns of speech - (can be you reading his work to him, or hom to you)...when your voice drops down, it's usually time for a period/full stop.AnNY you can take a breath!! And when your voice goes UP, it's usually time for a comma. Obviously a very general rule, but learning IS all about how finding out how rules workand don't work, isn't it!