you can use dbms_metadata.get_ddl to generate a script for you
select dbms_metadata.get_ddl('PACKAGE','YOUR_PACKAGE','YOUR_SCHEMA') from dual
or if you are using TOAD, go to the schema browser, right click on the package, click "Create in another Schema"
of course, the "best" method is to use the same script you used to create the object in your first environment to create it in your second environment
keep your scripts in a source code control system like CVS.