Agile software development
The best high-level description of agile and how the different pieces fit together (such as Scrum and Extreme Programming) I've come across is Agile Fluency from James Shore and Diana Larsen. If you'd prefer a video to a text, there's also an excellent talk from James Shore on the topic.
Nobody wants your stupid process
In the talk Nobody wants your stupid process, Jeff Patton makes note of a scale that goes something like this:
Generally, successful organisations make use of tricks and techniques, and are able to adapt to different situations, making good use of what they already know while being inventive at the same time. The more you edge towards process and methodology, the less room you tend to have for creative thinking, and coming up with new ideas. That's not to say that process is automatically bad, but it has a cost that has to be justified.