I think the simple answer (crudely summarising what is written above) is: “don’t put items in containers – give them tags instead”. (OK, horribly simplistic, but for someone who is just starting, it might be best to cut to the chase.)
I started a whole thread some time ago which you might find useful, as it discusses ways of working with meta data. See: http://forum.eastgate.com/t/user-attributes-or-tags/1069.