Here is a growing collection of tips, tricks, and techniques for the Arduino.
How do I Power my Arduino? - Robocraze
ArduinoISP, Arduino Tips, Tricks, and Techniques
Arduino Programming Software Development
A Beginner's Guide to Arduino : 15 Steps (with Pictures
Effective coding techniques in Arduino: More about datatypes
5 Tips for Arduino Programs, Articles
The Absolute Beginner's Guide to Arduino
Arduino Software Interrupts
ArduinoISP, Arduino Tips, Tricks, and Techniques
Arduino With Python: How to Get Started – Real Python
Adding many sensors to one board - Programming Questions - Arduino
Arthur, James: : Books
Arduino: The complete guide to Arduino for beginners, including projects, tips, tricks, and programming!
How to Code Your Arduino Board
Unleash Your Arduino Uno Projects: Avoid Sensor Tips And Tricks