Tesco and McDonald's are just two global brands that are trying to deflect their (potentially unfair) detractors' qualms by pursuing CSR.
CSR and 'going green' should not, initially, be for publicity purposes. Paying invoices on time, ensuring adequate maternity leave, non-exploitation of suppliers, trying to reduce energy consumption, for example, should be core to a brand's internal ethics.
My advice to any organisation is to develop an internal CSR policy and religiously implement it. These ethics may filter out to the greater community, but hopefully not via some advertising slogan.