The Real Meaning of Agile
Doing something in an agile way means making a small change quickly, learning from it, making adjustments to our understanding of the problem and repeating this many times.
This is what doing something with agility means:
What to do:
Find out where you are
Take a small step towards your goal
Adjust your understanding based on what you learned
How to do it:
When faced with two or more alternatives that deliver roughly the same value, take the path that makes future change easier.
These few simple steps are really what agile is all about. Stick with these basics and you can apply them to all parts of software development:
When writing code, do it in an agile way. Decide what you want to achieve, do a small change, test it, learn from it, adjust and repeat. Try to write code that's easy to change later.
When building a product, do it in an agile way. Do small changes, get immediate feedback, do small iterations and make decisions that allow future changes as much as possible
Similarly, when working as a team, solve problems using these basic principles, a small step at a time
The tools and methodologies you use should help achieve this kind of agility. If they only add more process - remove them.
The most successful engineers, teams and products all follow these simple steps one way or the other. Agile is not a methodology with rules and processes to follow. At its roots agile is a simple and fast way of learning and improving by taking small steps, one after the other.