I'd like to contribute to Ubuntu development some day. If you're a developer of Ubuntu could you tell me/us what are the prerequisites to start?

What languages and technologies are needed to know, how to make familiar with development (overview over the project) and development process? I am interested in the core of the distribution, the main parts, not writing applications.

I'd like to read some advice from the developer who has already some experience and can say the main points of his learning path and difficulties (that are general enough for typical Ubuntu distribution developer) he had to overcome.