Agile is an attitude: https://blog.cognitect.com/blog/2017/7/27/how-we-work-agile-is-an-attitude (on the value of agile techniques, but applying them with an awareness of their limitations)
miniblog.
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Individuals and interactions over processes and tools => Competence trumps process
Working software over comprehensive documentation => Minimize time from program launch to deployment of simplest useful functionality
I really like the DoD's phrasings of classic agile maxims:
I've built a simple personal wiki/blog at https://notes.wilfred.me.uk/. It has few features and little content, but it works.
I've tried to apply an agile philosophy: ship it ASAP. This is hard for side projects. I found the features I wanted after shipping changed considerably!
OH agile philosophy: "postpone decision making until the last responsible moment"