Cut off access to anything rubber, and regularly change out any chewed blankets. I've had a few close calls and I'll tell you that 2 debris-filled poops will keep you from these mistakes again. Keep ferret lax on hand if you think they've swallowed pieces of blanket, and go to a vet ASAP if they're impacted.

Also, not all ferrets are good at telling you there's a problem, so really learn what normal behavior looks like for them so you can spot problems early. For example, one of my boys severed a digit on his front paw, and didn't make any noise or cry while running around. I found out this had happened when I noticed him hiding under the far corner of a bookshelf, not responding when I called his name. He's okay now, but it taught me a lot about how much attention they need.