The practice of the night has been explained in The Practice of the Night and the Dark Retreat of Twenty-Four Hours (paper version, e-book)
In Dzogchen teaching, the practice of Guruyoga is indispensable because it is the root of all practices; if we follow the teaching, the first thing to do is Guruyoga. Some people learn highly complicated methods and are satisfied with that, but they do not do Guruyoga; this is not good, because in that case it is as if the root of the teaching is missing: the connection to the teacher and the transmission. Guruyoga practice according to Dzogchen means going directly to the essence. In fact, the teaching explains that the condition of Buddha or the dharmakaya coincides with our profound nature, so there is no need to look for it outside of ourselves. The word Guru indicates the understanding we receive from the teacher, which is nothing other than the teacher and our real nature. Guruyoga means to actually be in that state with him in the same instant. There are many practices that go by this name, but the essential meaning of Guruyoga is to be in the state of instant presence that you were first introduced to by your teacher. Guruyoga permits us to find ourselves in that state again. The first part of this book contains a general explanation of Guruyoga, its meaning and its aspects related to view, meditation and behavior. The second part contains the Guruyogas mostly applied in the Dzogchen Community, the methods for introducing the rigpa state and the empowerments for the Guruyoga worldwide transmission.