This is the first of a series of blog posts that deals with Plone migrations.
Stefan Holek gave a great presentation at the Plone Conference 2006 in Seattle about mistakes and things to avoid when programming with Zope & Plone.
As a developer you should take your time and step through the slides:
I am sure that even advanced programmers will find violations of the 28 Lurker Laws in their code. This is a must-read.