What is the procedure to file PIL? What kind of expenditure is expected in a PIL against the central government for environmental related issues?
Any citizen of India can file Public interest litigation either before The supreme court of High court. There is the same procedure for filing PIL in both courts. Article 32 of the Indian constitution provides a fundamental right to every citizen to file writ or another proceeding before the Supreme Court for the enforcement of fundamental rights conferred in part 3 of the constitution.
Filing of the writ for the enforcement of fundamental right is also a fundamental right so the court cannot entertain it ordinarily. Article 21 of the constitution recognises a clean and healthy environment as a fundamental right. MC Mehta vs Union of India AIR 1999.
For the filing of PIL, you have to establish before the court that cause of action is related with the large public interest and you have locus standi to bring this cause of action before the court by way of PIL. No formalities are required except to give notice to the concerned department of the Government before the filing of PIL.
You can send a letter to the Chief Justice of India or Chief Justice of the High Court with details, if the court finds that there is an issue related with large public interest then the court can take your letter as a PIL (H A Khatoon vs the State of Bihar, Dhirendra Chamoli vs Union of India).
Supreme Court of India issued guidelines on 01-12-1988 regarding PIL as Petitions about environmental pollution, disturbance of ecological balance, drugs, food adulteration, maintenance of heritage and culture, antiques, forest and wildlife and other matters of public importance will ordinarily be entertained as Public Interest Litigation.