Specialised consultancies can support in that area. Also development banks have a lot of experience. So you could partner with such companies or reach out to employees of such companies / organisations and ask for advise.
It would be important to check if the company has a ESG policy and framework, what is the work that they have done on ESG as the policy should not merely be on paper but put into action and there must be genuine committment. It will also be a good idea to have an external agency conduct an audit on ESG for the target company. Also look up on the ESG reputation of the company, if any environmental violations have taken palce, any legal matters in the court on ESG/governance etc.
With reference to ESG and Trippel Bottom Line accounting (or 3P – People, profit, planet) what is the metric that the target is tracking / reporting on ?
Assuming that the basic framework / policy is in place.