Make sure everything is CLEAN_CLEAN_CLEAN when you bottle AND when you do the primary ferm. It doesn't take much to give a good beer an off flavor. Soap is awful in beer. And a little wild yeast in the brew and really mess stuff up.
I throw my bottles into the dishwasher (without detergent) and run them through a 'Sani' cycle. Works like a charm, and it's easy!