If you want to know how make your wordpress more extendable and flexible you should definitely consider different resources and guides that are dedicated to developing wordpress plugin from scratch. Today we’ve prepared a list of the most essential resources for those who want to become more acquainted with building wordpress plugins.
3. Easy WordPress Plugin Development (Part 1-5)
28. Real-Time Plugin Development (more advanced plugin developmet)
29. Intermediate Plugin Development (Learn how to write a great WordPress plugin using intermediate plugin development techniques)
Last but not least
32. Writing a Plugin