Generally it is said that there are only three things that benefit the deceased after his/her death:
1. Sadakaqatul Jaariyah (Ongoing Charity) - e.g. An Educational institute or scholar or anything still beneficial to the community
2. Beneficial Knowledge - Having taught someone something beneficial
3. A righteous child praying for them. - A child that continuously prays for their parent for forgiveness
Furthermore other beneficial activities include:
1. Covering the debts of a deceased person
2. Making Charity on their behalf
3. Sacrificing an animal and distributing the food to the poor on behalf of the deceased
4. Honouring the last wishes of the deceased (e.g. Their Will especially any Waqf (special wishes)).