Supreme Court, in Guruvayoor Devaswom Managing Committee v. C.K. Rajan  7 SCC 546 though laid down the following guidelines in relation to public interest litigations:-
(i) The Court in exercise of powers under Article 32 and Article 226 of the Constitution of India can entertain a petition filed by any interested person in the welfare of the people who is in a disadvantaged position and, thus, not in a position to knock the doors of the Court.
(ii) Issues of public importance, enforcement of fundamental rights of large number of public vis-a-vis the constitutional duties and functions of the State, if raised, the Court treat a letter or a telegram as a public interest litigation upon relaxing procedural laws as also the law relating to pleadings.
(iii) Whenever injustice is meted out to a large number of people, the Court will not hesitate in stepping in Articles 14 and 21 of the Constitution of India as well as the International Conventions on Human Rights provide for reasonable and fair trial.
(iv) The common rule of locus standi is relaxed so as to enable the Court to look into the grievances complained on behalf of the poor, the deprived, the illiterate and the disabled who cannot vindicate the legal wrong or legal injury caused to them for any violation of any constitutional or legal right.
(v) When the Court is prima facie satisfied about variation of any constitutional right of a group of people belonging to the disadvantaged category, it may not allow the State or the Government, from raising the question as to the maintainability of the petition.
(vi) Although procedural laws apply to PIL cases but the question as to whether the principles of res judicata or principles analogous thereto would apply depend on the nature of the petition as also facts and circumstances of the case.
(vii) The dispute between two warring groups purely in the realm of private law would not be allowed to be agitated as a public interest litigation.
(viii) However, in an appropriate case, although the petitioner might have moved a Court in his private interest and for redressal of the personal grievances, the Court in furtherance of the public interest may treat it necessary to enquire into the state of affairs of the subject of litigation in the interest of justice.
(ix) The Court in special situations may appoint Commission, or other bodies for the purpose of investigating into the allegations and finding out facts. It may also direct management of a public institution taken over by such committee.
(x) The Court would ordinarily not step out of the known areas of judicial review. The High Courts although may pass an order for doing complete justice to the parties, it does not have a power akin to Article 142 of the Constitution of India.
(xi) Ordinarily the High Court should not entertain a writ petition by way of Public Interest Litigation questioning constitutionality or validity of a Statute or a Statutory Rule.