QUESTION: How does the mind go from one body to another?
ANSWER: Think of it being like radio waves. The radio waves, which are not made up of words and music but energy at different frequencies, are transmitted, travel through space, are attracted to and picked up by the receiver from where they are broadcast as words and music. It is the same with the mind. At death, mental energy travels through space, is attracted to and picked up by the fertilized egg. As the embryo grows, it centres itself in the brain from where it later "broadcasts" itself as the new personality.

QUESTION: Is one always reborn as a human being?
ANSWER: No, there are several realms (界) in which one can be reborn. Some people are reborn in heaven(天), some are reborn in hell(地獄), some are reborn as hungry ghosts(餓鬼) and so on. Heaven is not a place but a state of existence(存在狀態) where one has a subtle body(微細身) and where the mind experiences mainly pleasure. Some religions strive very hard to be reborn in a heavenly existence mistakenly believing it to be a permanent state. But it is not. Like all conditioned states, heaven is impermanent and when one's life span there is finished, one could well be reborn again as a human. Hell, likewise, is not a place but a state of existence where one has a subtle body and where the mind experiences mainly anxiety and distress.
　　Being a hungry ghost, again, is a state of existence where the body is subtle and where the mind is continually plagued by longing and dissatisfaction.
　　So heavenly beings experience mainly pleasure, hell beings and ghosts experience mainly pain and human beings experience usually a mixture of both. So the main difference between the human realm and other realms is the body type and the quality of experience.