1) Collect as many ERC proposals as you can get from friends and colleagues and scheme-read them to get a feel for what they look like
2) Download the templates and start filling out the forms.
3) Register at the ERC portal. It takes a long time and has a few steps – some of them legal and financial – and if you leave it to last minute this will cause you trouble.
3-1) talk to your Head of Department and ask for the Support Letter to be issued and signed as quickly as possible
4) Construct your 5-page summary and collect reviews from colleagues and the research office of your university. This latter one, administration feedback, is crucial.
5) consult your finance office and plan your costing. The most important part of this costing is your own Professorship and tenure status. If you have tenure then great. If not, then this is the place where you should negotiate your future (conditioned on ERC grant) with head of department and dean of university.
6) here you can find my own ERC proposals (B1 and B2 – stg and cog)