Currently, there are 2 prominent project management methodologies/theories. Waterfall and agile. Most common is the Waterfall based upon PMI (but also Prince2), and agile based upon Scrum (but also Extreme Programming, Crystal Methods, Kanban etc).
Please note that very few organisations employ a pure methodology as described by the corresponding theories. There are 2 main reasons for this:
- Corporations are seeking for a competitive advantage. If all were using the same methodology then they wouldn’t have an advantage. Therefore they always explore further, and as a side-effect theories are further improved.
- There is always a gap between theory and praxis. Simply speaking usually there is either a lack of education or resources (time, money, manpower …) in order to implement the corresponding theory. Or simple enough the theory does not fit our case.
Personally, I do not find anything more practical than a good theory! The familiarity, and ability to implement various theories is a great asset to tackle problems.