Chanting Nam Myoho Renge Kyo (called Daimoku) happens when we do Morning and Evening Gongyo (Sutra recitation). But there may be times during the day when you want to chant extra. We refer to this as doing “Shodai.” You can chant by yourself or you can chant with others.
Fifty-ninth High Priest, Nichiko Shonin, stated the following on the practice of Shodai:
“The Daimoku that we chant must be performed attentively and diligently. When chanting, we should not have trivial thoughts in our minds. The speed should not be too fast and our pronunciation should not be slurred. We must maintain a medium pitch and chant calmly, resolutely and steadily. There is no established number of Daimoku that we must chant. The amount depends on individual circumstances. . . . When we chant, the entire body should feel a tremendous surge of joy. We must persevere until we become totally one with the Gohonzon.”
(Nichiren Shoshu Koyo, p.134)
More information about how to perform Shodai can be found in the Nichiren Shoshu Basics of Practice book, pages 18-19.