Managing Code - Creating a Library/Package from scratch?

The bit I always struggle with on various Smalltalk environments is the right way to manage code.  It keeps changing.  Which is fine. But I've been away for a bit and I'm lost now.

I want to create a new package that can be loadable and lives in a git repo.  I guess Metacello is part of that.  And Iceberg. And...what else?  I want to build a library but am no longer clear on what a library (or package I guess) definition is built from.

Thanks.