The enclosure of a boa has to be at least 3/4 the length of the snake at adulthood, and at least 2/3 as wide as the snake is long. Please not that an adult snake measures 8 feet and up, sometimes you get snakes longer than 10 feet. The ideal size of the enclosure should have at least 3/4 sq foot per foot of snake. The temperature at night should be 80 degrees farenheit and 85 degrees in the day. The snake should have a basking area of about 90-92 degrees farenheit. The substrate should not include cedar. For a simple substrate, you can use blank newspaper, most printing facilities will sell this to you per roll. If you want something more atractive, use carpeting, keep a couple pieces handy so you can always have a clean piece while you are cleaning the cage. Do not use Lysol or Pine, these leave residues which can kill your pet. Use a diluted forem of bleach(about 3-5% bleach), rinse and dry thouroughly before using that piece of carpeting again. If you wish to have a bedding are, aspen is what I recommend.
The boa constrictor eat's a variety of rodents. A newborn snake should eat every 5 days. Start with baby mice or rats, and as your snake grows feed it larger animals. When your snake get's larger it will feed less often like every 7-10 weeks. An adult snake will feed every two weeks to once a month(If your snake sheds once a month, he is eating the right amount), and eat a large guinnea pig or a rabbit(Note that rabits will scream). Use of a vitamin supplament is an option. Your local pet store will probably carry this. Avoid handling your snake after feeding until the lump goes away.
When handling your snake, make sure you have another adult around, as a your snake, if it constricted you, could very well kill you. When you hanlde your snake, don't make very fast movements, and don't handle it rough. Let it wrap around your arm for support, or it might feel nervous or threatend. When removing your snake and putting it back in it's cage, have someone help you.