Practical Production Control: A Survival Guide for Planners and Schedulers

Read The Goal and Critical Chain by Goldratt, but with several grains of salt. Most of the stuff is good, common sense. It must be interpreted, assumptions understood, and compromises appreciated. Few things are as black and white, or as extreme, as described.
Focus on the bottlenecks. Think about how you are using them and what the wasted aspects are. Invest in them and the supporting departments that are associated with them. Do not focus on areas that do not help the bottleneck!!!
Watch for the moving bottlenecks and the critical resources that feed bottlenecks. What you think is the bottleneck today might not be the bottleneck tomorrow. A nonbottleneck resource can starve a bottleneck if production is disrupted and insufficient inventory exists.
There are a number of things you need to think about when considering bottlenecks, and often issues at bottlenecks consist of interdependencies. You will need to fix many things before an improvement will be seen.
Whole books can be, and have been, written on bottleneck management. For example, in The Goal, Goldratt refocused manufacturing in the mid-1980s on bottleneck resources. He addressed similar issues in Critical Chain for project management. These two books should be read. Whether or not you agree with everything stated, or all of the claims, he forces you to re-evaluate your thinking. At the time, manufacturing had lost sight of bottleneck management and Goldratt helped people realize that bottlenecks gated the whole...