When choosing the right size habitat for a pet snake, you should consider the species and size of the snake. Generally, the enclosure should be at least as long as the snake when fully stretched out, with enough room for them to move around comfortably. Additionally, the habitat should have adequate heating, lighting, hiding spots, and proper substrate for the snake's needs. It's important to research the specific requirements of your snake species to ensure you provide the appropriate size and type of enclosure for their well-being.