In a nutshell, Lean says to relentlessly eliminate anything that isn’t adding value and only work on what we absolutely need to be doing at this moment in time. Eliminating waste means eliminating useless meetings, tasks and documentation. But it also means eliminating time spent building what “we know” we’ll need in the future (things are constantly changing so we often end up not needing them – or if we do, we have to rework them because conditions and our understanding has changed by then). It also means eliminating inefficient ways of working – like multitasking (!) – so we can deliver fast.
Lean also puts a very strong emphasis on what it calls “the system” – that is, the way that the team operates as a whole. We always need to be looking at our work from a top level to ensure we’re optimizing for the whole. For example, many managers want to “optimize” individual developers by ensuring they’re always at 100% – but most of the time, this is actually counter-productive. Let’s not have people coding something that isn’t needed (or fully defined yet) just for the sake of coding, because that actually creates more work for us in the future (see: Why You Should Let Your Developers Surf).