In this post I will show you how to pre-populate data from the parent record when a child record is created from the related list. Some Geeky people may have already know this, but this is for Newbie people in Salesforce. So, Let's Started.
I will break the work into following parts:
1. Creating Field on Child Object.
2. Creating a Custom List Button.
3. Adding Custom Button to the Parent Page Layout Related List.