Ngöndro are the foundational practices that precede advanced tantric training. They begin with contemplations of precious human birth, impermanence, karma and suffering, and continue with prostrations with refuge, the mantra of Vajrasattva, maṇḍala offerings and guru yoga, each traditionally performed a hundred thousand times.
Ngöndro
The preliminary practices of Tibetan Buddhism: refuge, purification, offering and guru yoga, each done many times.
Also: preliminaries