In terms of Article 11.4 (TEU) and Regulation 211/2001 over 1 million citizens can demand a European law. The Commission has a dedicated website describing how European Citizens’ Initiatives (ECIs) work and the state of play with successful, refused or failed ECIs.
If you want to find out which ECIs you can sign, there are links to them from the Commission website.
A number of NGOs offer assistance with ECIs:
Each year the European Economic and Social Committee brings the main stakeholders together in April.