A very neat way to create a list instance is through a feature.
For eg you have list definition with a feature ID
you need to create another feature suppose list instance
in this feaature folder you will have an instance.xml whi will contain information likee
1. name of the list instance you want to create
2. listtemplate feature ID
now as soon as this feature is activated on any web a list with the name you specified and of the type you selected would be automatically created