Yom Kippur does not atone for sins between man and his fellow. Therefore, if one wronged someone, even in words, he must make amends prior to Yom Kippur.
A. How to ask for forgiveness:
In front of three: One should ask forgiveness from the person he offended in front of three people.
Mentioning the sin: One must explicitly mention to the victim the sin or offence that he is asking forgiveness for. If, however, the victim will be embarrassed to hear the sin or offence, one is not to mention the particular sin and is rather to ask for general forgiveness.
If the person is no longer alive: If the person one offended is no longer alive, then if the grave is within a three Parsa distance, one is required to go barefoot to the grave together with ten other people and ask forgiveness from the deceased. If the grave of the person is further than a three Pars distance, one may send a messenger together with another ten people, to the grave to ask forgiveness from the deceased.
B. To forgive the offender right away:
When asked for forgiveness, one must forgive the offender immediately. One must be careful in this matter especially at this time of year, prior to Yom Kippur, as when the Jewish people are unified with one heart, the Satan cannot prosecute us.
Forgiveness for the sin of Motzi Sheim Ra: When being asked for forgiveness from a person who slandered him through spreading false rumors [Motzi Sheim Ra], he is not required to forgive the asker at all. Nevertheless, it is an attribute of mercy to forgive the offender even in such a case.
If the assailant is not truthfully remorseful: If one sees that the offender does not truly have remorse, then he may refuse to forgive him in order to cause him to feel remorse for what he did.
C. How many times must one try to appease the person he offended?
If the victim refused to forgive the offender after he approached him for forgiveness, the offender must try to appease him another two times in different ways. If the victim still refuses to forgive him, the offender is no longer obligated to try to appease him. Nevertheless, he must tell ten people that he has asked for forgiveness from the person he offended and the victim refused to be consoled. If one desires to be stringent and continue to try to appease the person he offended, he may do so even one hundred times.
One offended his Rebbe: If one offended his Rebbe, even if this is not his main teacher but rather one from whom he has learned Torah, he must try to appease him and ask him for forgiveness even more than three times, until he receives forgiveness.
 Admur 606/1
 Admur 606/2
 Admur 606/1
 Admur 606/5
 Approximately 5 hours of walking.
 Admur 606/3
 Admur 606/8
 Admur 606/4; Rama 606/1; Semag Asei 16; Yerushalmi Bava Kama 8/7
 The reason: As forgiving him may mislead people to think that the slander was true. [See Admur ibid]
 Admur 606/4
 The reason: As one’s own life comes before his friend’s. [Admur ibid]
 Admur 606/4
 Admur 606/2-3; Michaber 606/1
 Admur 606/2; Michaber and Rama 606/1
 Admur 606/3; M”A 606/2; Bach 606
 Admur 606/3; Michaber 606/1; Yuma 85b