Picturing the name of Hashem in one’s mind:[1]
It is written in the name of the Arizal that one should accustom himself to vision the letters of the name of Hashem [Yud Kei Vav Kei] in his mind as this is of great assistance in bringing a person to fear of G-d.
[1] Beir Heiytiv 1:2; Kaf Hachaim 1:2 in name of Shaar Ruach Hakodesh 21; Ketzos Hashulchan 144 footnote 6 states that his uncle Reb Dovid Tzevi Aryeh Schneerson told him that the Gaon of Brisk would periodically write the name of Hashem in the air in order to fulfill the verse of “Shavisi Havayah Linegdi Samid”.