Lean manufacturing is not a new concept. In fact, its been practiced and nearly perfected over the last 100 years. It started in the early days of manufacturing when companies were trying to figure out how to build more parts faster and cheaper and with less waste. It eventually found its way into the form of an assembly line and worked its way into post war Japan and back to the US in recent decades. It's never flawless, however trying to get better is the principal goal.
This idea of continual enchantment is what drives lean manufacturing forward. You need to have the ability to look at the whole process from starting point to end point and decide what is going to be able to be improved and what isn't cost effective to improve. Some things have to be performed and there is only one way to do it and it just can't be improved upon. There are also things which you have to do, such as office work and duties that are not directly related to adding value to your product, nevertheless they still have to be performed.
These things shouldn't be ignored, however they should be grouped separately and concepts for these non-manufacturing processes should be looked at. They will just have to be carried out differently and by different workers. The processes that add direct value to your product and therefore your customer are the most significant things at the moment.
These processes, from beginning to end make up the production of your product. They include ordering the parts needed or manufacturing your own parts and not building everything until it is ready to leave your facility and into your customers hands. Surely there are things that you could point out right now that aren't really efficient. There are probably ten ideas in every persons head on the floor to resolve the obstacles.
But, you have to be willing to find and evaluate these problems and be willing to correct them to the best of your effort. There are a lot of ways to go about recognizing the problems and deciding which ones to revamp, however you need the biggest bang for your buck. You need return on investment.
You also want to fix the problems or change the processes that make the most trouble. What is causing the most trouble and problems should be looked at first. That way you don't have anything holding the other changes back.