1 Fulfilling and performing all the obligatory duties on time. Like prayers fasting khums Zakat Hajj etc.
2 Compensating the missed obligatories of the past.
3 Returning back the rights of others and seeking forgiveness from everyone who has been wronged or harmed by us wether intentionally or unintentionally.
4 Performing the night prayer Salat Al Layl ( Namaz e Shab) as it has got a great benefit in purifying the heart and omitting the sins.
5 Repeating " ASTAGHFIRULLAH'' or ASTAGHFIRULLAH Rabbi wa ATOOBU Ilayih. Especially at night and more especially in the state of sajdah.
6 Seeking the supplication of your parents for your forgiveness, even if they are dead, by visiting their graves and praying there.
7 Reciting Ziyarat Ashura every day.
8 Repeating Salawaat as many times as possible.
9 Praying for the forgiveness for you and all the believers who are dead or alive, including believers who have harmed you.
10 Reciting Sura Al Qadr while performing Wudu, as the Hadeeth states that it is a great way to get our sins forgiven.
11 Arranging, helping and attending Majaalis of Ahlulbayt AS and weeping for their tragedies that they suffered.
12 Paying charity for the sake of Allah on behalf of Ahlulbayt AS.
13 Reciting the Munajaat of Al Sahifa Al Sajjadiya, Munajaat al Mustagfireen.
14 Reciting Sura Tawheed after every Salah.
These are few acts to gain forgiveness and there are many more.
Wassalam