Question: what is the major reason that cats are surrendered to shelters?
Answer: house soiling.
For the above reason, I would consider house soiling (which includes inappropriate urination and spraying) as a life-threatening condition for a cat. This is a complicated topic with adult cats that have already developed the problem, and unfortunately it is not always easily fixed. However, there are some things we can do with out kittens to hopefully avoid this problem further on down the line.
What should we as owners be doing for our kittens right from the start? First of all, we need to understand that kittens don't have a strong location or substrate (litter) preference right off the bat and may not have motivation to go searching for sand or litter to dig around in. Litter boxes should be easily accessible in a convenient location. Kittens, especially shy kittens, may view dogs, other cats, or humans as barriers. They may be frightened off by noisy appliances. Cats also have very sensitive noses and may be put off by odors. Take care in choosing the location of the litter boxes and try to see what it may feel like to the kitten. Clean the litter box daily if possible. If not, the kitten may go searching for a clean, absorbent surface (clean pile of clothes, anyone?) Other popular targets are empty bags and boxes.
If your kitten is already eliminating inappropriately, take steps immediately to intervene. Medical conditions may be the culprit and veterinary consultation is recommended!
Lindell, Ellen M. "Top 5 Kitten Behavior Tips." Clinician's Brief Feb. 2016: 24-26. Print.