One can honour his parents after their death through the following methods:
1. Performing daily Du'aa' (supplication) for them.
2. Giving charity on their behalf.
3. Instituting a perpetual charity on their behalf, such as a mosque, an Islamic Centre, an Islamic library, an Islamic hospital, an orphanage, etc.
4. Performing Hajj on their behalf, or asking someone to do so.
5. Distributing Islamic literature on their behalf.
Let us pray to Allaah that we do our best to respect our parents, honour them, be kind to them, assist them, and please them so that we may attain the love of Allaah.
Accept our humble prayers and make us obedient slaves to You.
Help us to be respectful children to our parents. Aameen.