Choose a rabbit with body-friendly silicone on all parts that come into contact with the body. Silicone is non-porous and easy to keep clean. Most models have a handle made of hard plastic, often ABS, which is non-porous but sounds and feels different.
Look for an explicit material declaration. We-Vibe states that Nova 2 is manufactured without phthalates, BPA, and latex, and Fun Factory states in its FAQ that its products are free from softeners, BPA, and phthalates. Not all manufacturers publish it: for Mono Flex, DuoGlow, and Pro G-spot Rabbit, no such declaration is published, which doesn’t mean the substances are present, but that the commitment is missing. More about the materials is in "safe materials in sex toys.
Use a water-based lube. Silicone-based lube can break down the silicone surface, and LELO warns in the Ina 3 manual that silicone lubricants and hand cream can make the silicone permanently tacky. Don’t use a rabbit anally—several manufacturers, including Womanizer for Blend, explicitly state that their models are not designed for that.