What websites, books and other sources are a good reference for the process of electronic product design?

I have worked in electronics product design as a technician and would like to know of any good sources of information about the process of product design.

I know about the ISO testing standards and what each entails but would like a kind of checklist that explains step by step how to go about this.

I assume a spec is written followed by a prototype but not totally sure.

Has anyone got any ideas for me please?