How to introduce animals to new baby?

I've never had to do this. With my oldest, his father had a dog, older in age and he didn't care too much for baby so it wasn't a big deal and didn't have to do introductions. I have a 5yr old dog who acts like a puppy when she's beyond excited but she is very calm and collective and I have a 4yr old cat and a 1 and a half year old cat. The 4 year old can careless about anything lol actually has become more loving lately, and my 1 and a half year old still acts like a baby because that's what she is, I have caught both cats in baby's crib and my younger cat has this obsession for his bassinet she thinks it's hers. My dog isn't my fear it's my cats. They aren't allowed in the rooms because I don't want dirty paws and cat hair on his stuff. But how can I get them used to baby "all my animals never been around babies" before baby is here or when he is here? Help!