Our developer’s documentation has a lot of information to get you started. We’re continuing to build and beef up this portal, but you may find most of your answers here:
Other useful stuff.
ScottinPollock’s video tutorial on Creating SmartApps from External code
Terminology Is Important: Documentation Needs a Glossary?
Listing all set parameters
@JDRoberts has a great explanation about Modes and Hello Home Actions in a coder’s POV and how it affects the end-user.
I use ‘Light Turn On Motion’ Smartapp, I want to edit that code but I can’t find it on IDE menu. Where is it ?