How can a Shi’i become one of Ahl al-Sunnah wa’l-Jamaa’ah?

If a person was following
an ‘aqeedah that is contrary to that of Ahl al-Sunnah wa’l-Jamaa’ah, such as
the belief that the Qur’aan has been altered, or that the imams are
infallible and can bring benefit or cause harm, and their help is to be
sought at times of hardship, or the belief that all the Sahaabah except a
few apostatized, or the belief that some people will be resurrected before
the Day of Judgement and that Allaah may change His mind (when new facts
emerge) and that Ahl al-Sunnah are kaafirs, then the way for him to repent
and become righteous is to give up these beliefs, and adopt the beliefs of
Ahl al-Sunnah which is belief in the Oneness of Allaah (Tawheed) and not
associating anything with Him; venerating the Sahaabah, loving them and
approving of them; believing that the Qur’aan is sound and free of
distortions, additions or subtractions, basing his belief on evidence from
the Qur’aan and Sunnah as understood by the early generation (salaf) of this
ummah. 

For more information on
beliefs that are contrary to that, please see the answer to question no.
60046,
44970,
101272 and
95588. 

And Allaah knows best.