Create a .pkg file from a .dmg in order to be used for auto-install ( Casper Composer ) I would like to create a .pkg file using the Casper composer but  i don't know which files of the .dmg to include .

I appreciate your help .
Try http://resources.jamfsoftware.com/documents/products/documentation/Composer-9.7-User-Guide.pdf page 12:

Composer allows you to rebuild an existing package (PKG, DMG, or MPKG) by converting it to a package source. After converting it to a package source, you can make changes to its contents and save a new copy of the package.


Open Composer and authenticate locally.
Drag the package you want to convert from the Finder to the sidebar in Composer.
The package appears under the Packages heading.
Select the package and click Convert to Source.
When the conversion is complete, a new package source is listed in the sidebar under the Sources
heading.