As per the scriptures, a right guru must be fulfilling two important qualities:
- Srotriya : He must be well versed in all the sashtras, i.e. Vedas, Puranas, Philosophies, etc. (master in theory)
- Brahmanistha: He must himself have realized God and stays fixed in Him. (master in practice)
So the scriptures say as below:
tad vijñānārthaṃ sa gurum evābhigacchet samit-pāṇiḥ śrotriyam brahma-niṣṭham [Mund. Up. - 1.2.12]
-To know That (God) he (the seeker) goes to a guru who is well versed in scriptures and situated in Brahman (God realized) .
tasmād guruṃ prapadyeta jijñāsuḥ śreya uttamam
śābde pare ca niṣṇātaṃ brahmaṇyupaśamāśrayam [SB - 11.3.21]Maning
Therefore, the seeker approaches a good and noble guru who is skillful in the knowledge of the scriptures and the supreme and who having taken the shelter of Brahma stays satisfied in Him.
After following a guru for few years if you find you are not improving or he is not the right person, then the only thing you should do is to stop following him and without any ill feelings towards him, just try to find someone else.
Technically one can do a lot of things after he finds himself cheated or a prey to the media hype, but he should focus upon continuing his development rather than getting revenge minded and focusing on someone else's ruin. Those negative feelings will only degrade him further instead of helping him move up.
Finding guru is actually a subjective thing. Even while one guru may work for a seeker, he may not be good for another one. And again, how would you know if he is God realized? Any one may show some cheap miracle or some spiritual power and can act as a guru. So it is generally said that it is not the student who finds the guru, it is the guru who finds the student. For example, Vivekananda first didn't accept Ramakrishna as his guru, even he mocked him. But later upon more interaction he felt his divinity and accepted as guru. So without properly analyzing it is very hard to find out who is a true guru and who is not. It is because true saints even act opposite to their nature sometimes. So from my experience I would say if one has faith in God and genuine interest, then eventually he will find the right guru even if he falls prey to others many times.