The Four Celestial animals represent the ideal Feng Shui location. You can read more about the four celestial animals formation here.
In the ancient text the black turtle hill is often shown sitting north and facing south. China is located in the northern hemisphere and are exposed to cold winds from the north, hence having a mountain in the north to act as a shield is beneficial. The south is a source of heat and again it is beneficial to have a southern exposure.
However if you live in the tropics then it is not absolutely necessary to have a house that sit north and face south.
Regardless of the facing or sitting direction of the house, the turtle is always at the back while the Green Dragon is always on the left hand side of the facing direction which the White Tiger on the right.
In Feng Shui, the Green Dragon symbolizes the male while the White Tiger symbolizes the female. A house with a stronger Green Dragon side is believed to be beneficial to the males in house. The Green Dragon also symbolizes good relationship and prosperity.
The White Tiger on the other hand symbolizes the female, poor relationship, loss of money and misfortune. This leads to the belief that occupants of houses with a strong White Tiger have less money luck and poor relationship. They also produce domineering females.
Based on my experience, I do not find this to be entirely true!
The Red Phoenix in the front of the house should ideally be the same level of slightly lower that the house. If a slow meandering river or lake is not available, an open field can substitute for the Red Phoenix.
(Four Celestial Animals Trivial: The Red Phoenix can be a table mountain. It is mountain that is not high, sort of at eyebrow level!)