What's your approach to starting a new extension?

We create a lot of extensions. Most are small-time plugins or modules for clients, but we do the larger component releases every few months (or try to at least).

Since there is a lot of 'required, but same' code across a component, we created an internal tool to create the framework/skeleton of a component for us. We can input a table name, columns, and a few other niceties and the basic output will be the front-end and admin table, model, and view files which allow for listing and editing the rows in a table. The next step is then to gut this code and start making it do what we want it too.

Our generator is useable to 'us', but not to the rest of the world in its current state. Not sure if anyone would want it anyways. We've also be recently investigating Nooku as it cuts down a lot on the required 'standard' code for an MVC development. However, with library frameworks, there's other concerns we have, though it's very impressive in its current state.

Anyways, really just trying to figure out what other people's best approach to starting a new extension is? Start from scratch, modify something existing, other?