Recommendations abound about altar permanence, location, and orientation abound.
Altars are individual and personal, designed by each practitioner to express their relationship with God, Goddess, and Spirit. But, since few of us can afford to devote an entire room to an altar, and there may be privacy issues with visitors or other family members, there are always some restrictions. My particular restrictions have to do with direction, location, and personal preference. I am lucky enough to have been able to convert a spare bedroom into a den, and my altar is located there. No only is it out of the way of visitors with whom I don't necessarily want to discuss my religion, but it also provides me with a private room in which to hold my rituals.