What is Meant by Offenseless Chanting?
The root of all offenses is insincerity. So first of all, if we are sincere then even if we are somewhat ignorant of all the rules and regulations Krishna will help us to gradually overcome the offensive stage.
The Sanskrit word for offense is aparadha, or "to be distanced from worship" (radhat arthat aradhanat-apagatah) There are sometimes three different categories of offenses given:
Nama-aparadha, or offenses in chanting the holy name. They are ten in number. In his Bhakti-sandarbha Srila Jiva Goswami elaborates on them. Also Bhaktivinode Thakur in his Harinama-cintamani does so extensively. You can find them enumerated in many places in Srila Prabhupada's books. The complete list is in Nectar of Devotion, Chapter 8.
The remedy for offensive chanting is more chanting while trying to avoid the offenses. Thus the chanting will become pure. Padma Purana states:
namany eva haranty agham
tany evartha-karani ca
Even if one chants the Hare Krishna maha-mantra offensively, one can avoid offenses by continuously chanting without deviation.
Please refer also to the Srimad Bhagavatam 6.3 ("Yamaraja instructs his messengers").
Seva-aparadha, or offenses in Deity worship. A complete list is given in Nectar of Devotion.
Dhama-aparadha, or offenses against the holy dhamas such as Vrndavan and Mayapur. A list of ten offenses very similar to the offenses against the holy name is given (from "The Color Guide to Vrndavana, The City of Over 5,000 Temples" by Rajasekhara dasa Brahmacari, Vedanta Vision Publications 2000):
1. To have contempt or disrespect towards the guru who reveals the holy dham.
2. To think that holy dham is temporary.
3. Commit violence towards any of the residence of the holy dham, or to any of the pilgrims who come here, or to think that they are ordinary mundane people.
4. To perform mundane activities while living in the holy dham.
5. Earning money by, and making a business of Deity worship and chanting the holy name.
6. To think that the holy dham belongs to some mundane country or provinces such as Bengal, or to think that the dham of the Lord is equal to a holy place connected with some demigod, or to attempt to measure the area of the dham.
7. To commit sinful activities while in the dham.
8. To consider Vrndavan and Navadvip different.
9. To blaspheme the sastras which glorify the holy dham.
10. To be faithless and to think that the glories of the dham are imaginary.
If one goes to holy places with a sincere desire for spiritual advancement, there is not much to worry about. Sincerity is the key in everything.
The main thing to focus on is our chanting of the holy name. Always respect the guru and all Vaisnavas. Even if Vaisnavas do not appear to be of good character we should offer them respect, even if we don't associate with them. Be sincere, beg Krishna, Srila Prabhupada, and all Vaisnavas for some glimpse of offenseless chanting. Give up duplicity. These are instructions our acaryas have given, and we should try to execute them with faith.