PDCA Management Cycle is one of the most basic theories for managers. If you make use of PDCA Management Cycle, you can handle any kind of projects and business to achieve goals well.
You just take one by one in order. After you finish A, you are supposed to work on a new P that comes from the first PDCA. You don't have to make a big progress or a revolutionary change at once. All you have to do is just to go round and round until the cycles make a big difference the sooner or the later.