This can be any sentence you like.......
My favorite is "God is Light". As I meditate on this sentence( repeating it endlessly in my mind) I visualize the light. I try to visualize the light in the middle of my forehead,, I let it spread to my heart, to my entire body, through the room. filling the house, the street, the city, the country, the continent until the whole world is ablaze with the light of Love.
Blessings, AchyTen