There is a Greek custom, that one when mentions the name of a deceased friend or relative in conversation, that one also adds: "may God forgive him", "may God rest his soul", or "of blessed memory".
Indeed, what a blessing one has if one has relatives and/or loved ones that remember to pray for God's mercy on their souls. Each time we do, it is adding refreshment to their eternal state, and I believe, an act of love which is unprecedented and often unrecognized in today's world...
While memorial services, in the Orthodox tradition, are an organized ecclesial effort towards this intention, I think that adding one of the above prayers to a person's mentioned name, in a heartfelt and humble manner, is also adding a prayer.
Also, when I hear a memorial in church for another, (who more times than none, I do not know), I offer the prayers for their soul with their family and the congregation, but I also silently remember my loved ones by name and add the prayers for them, as well.
In addition, whenever I ask for prayers to be commemorated at the holy altar for proskomide, I add a list of deceased family members along with the living. I try to not forget to give a list of names for the designated Saturday of the souls, and I also try to not forget to give their names at any monasteries I may be visiting.
Sometimes I feel that wherever I was deficient in my earthly display of love, (perhaps because that relative or friend was difficult for instance) I am offering my love in a much more significant way now.
I have only grown to fully appreciate the profound meaning of helping others in the afterlife in the past ten years because of the intensity of feeling my priest displayed in offering funerals and memorials. Others just seem to run through it in an obligatory manner. Besides this, I also came to realize the profound assistance we can offer the dead after reading the life of St. Xenia of Petersburg, who offered her young widowed life in place of her husband (donning his proud regiment's uniform, aiding the poor, becoming homeless herself and a 'fool for Christ') in order to help his unrepentant soul attain eternal life, as well as other stories.
I also came to realize the antithesis of such selfless acts of helping a loved one's soul in the account of Tsar Ivan the Terrible and how to be utterly ruthless to his enemies, he would not only kill them, but kill any and all of their friends and relatives so that his enemy/enemies would have nobody to pray for their souls! (Lord have mercy!)
Just my humble input...