CRM 4.0 needs some "help" when it comes to customisation. Although a lot of the customisation is done through the web interface there are a few areas where people have provided tools to make life so much easier.
These need a utility to register them; there's one with the Microsoft CRM SDK and that has worked for me for plugins.
For workflows however I've used CRMTool.EXE from http://www.patrickverbeeten.com
There are different ways of doing this; they can be 'downloaded' via customisations but the tool on http://www.patrickverbeeten.com makes life much easier - connect; edit and update...
This is invaluable - download it from Microsoft - even if not considering writing custom code as such!
There are also some good books out there with technical information; and many, many good blogs about CRM.