What are some ways to keep a dog from chewing on furniture?

Your puppy will only chew the furniture IF he has the opportunity. I strongly recommend you to get a crate for the times you cannot be there to supervise what he's getting into. You can put any number of products on the furniture, some of which might work, but most of which won't, if your puppy is left to his/her own devices. It's a question of 'dog proofing' your home - prevention is always better than cure. I'm a bit confused about whether you have your puppy already ..... "..... are looking into getting a little longhaired Dachshund..." and then ".... sour apple spray (definitely didn't work), but it's a good idea to set your home up before your puppy arrives and that should include having a crate available for the times you are out or doing other things. Just remember - puppies should not be crated for longer than 2 hours at a time, and adults not longer than 4 hours.