Prayer for the deceased is a celebration of life.
Light a candle (thin, non-church), pour a glass of milk, you may also put a photo of the deceased, and read 9 or 40 times:
«Truly. I commemorate (name) as a person who lived on Earth, I commemorate with the Word blessed and kind. Indeed, the remembrance of (name) is alive, may the soul of (name) be filled with the Light of that memory and shine with the Source sanctified. Truly!»