You love your pet, but it has behavior problems you don't like (the dog "uses the bathroom" in the house, or it jumps on people; the cat doesn't use the litter box, or scratches furniture). Those are the most common, and there are many others.
To fix the problem, you have to understand how cats/dogs think and why they do it before you can train them to do what you want. An animal's behavior is instinctive to it. Animals do not understand English, Spanish, etc. (Honestly, a lot of people expect them to!) You must consistently show your pet what you want, praise/reward, and keep working on it until the pet "gets it." It takes time, but it's worth it, and you and your pet will enjoy each other much more! Where to get HELP:
Cat behavior problems are usually scratching the furniture, improper litter box use (or not), and spraying.
a. SCRATCHING FURNITURE: Most cats can be trained to use a SCRATCHING POST and/or a CARDBOARD SCRATCHING BOX. Cats also like to scratch LOGS. Put the scratching post, etc., in front of the furniture the cat likes to scratch. Get a SPRAY BOTTLE and fill it with water (keep it fresh) and spray the cat when it goes for the furniture.
You can also spray the furniture with any non-staining citric (lemon) product because cats do not like that smell. If you provide your kitten with these items at an early age, they will learn to use them rather than the furniture. An older cat can also be retrained, and may prefer these items to furniture. DECLAW should be a LAST RESORT ONLY, and then only the front paws should be declawed.
b. LITTER BOX: Cats which suddenly change litter box habits and start relieving themselves outside the litter box may have a health problem. This should be checked FIRST by the veterinarian. If there's no health problem, there is something else bothering the cat. It could be you changed the litter and the cat doesn't like it, or you moved the litter box to a location the cat doesn't like, or there is something new in the cat's environment which is upsetting it, like a new cat/kitten, or dog. In the latter case, you MUST give the cat 100 PERCENT more attention than you give the new pet, and make sure it has its own litter box and dishes and bed. And remember, it may take two to six weeks for the old cat to adjust to a new cat, and if you got a dog, the cat may be afraid of it. Introduce new pets to each other gradually--keep them in separate rooms when you are not at home.
c. SPRAYING: Both male and female cats may spray when they are afraid their territory is being invaded by a newcomer. Female cats rarely spray, however. Neutering a male by the time it is 4 - 6 months should keep it from ever starting the spraying habit, but there is no 100 percent guarantee of that. Usually, though, the early-neutered male does not start spraying unless some of the factors mentioned above in "Litterbox" are present. If a cat starts spraying, you need to follow exactly the same advice given for a change in litter box habits above. You can buy products at pet stores to help remove stains and odor. A new product available at vet clinics is "FELIWAY." It supposedly works by putting "happy pheromones" where you spray it, and the cat thinks it's not necessary to spray the spot. The product reportedly really does work.
A visit with a psychologist can solve difficult problems. It is not like therapy for humans; probably one visit will take care of the problem. It will likely consist of a quick evaluation of the situation, and training YOU how to handle the animal's behavior. Check the phone book or ask a vet for a name. Fees are usually reasonable.
Don't give up on your pet until you have done all you can do. Your pet wants to understand and please you (especially dogs!); you simply have to learn how to communicate effectively with it, or work around its instinctive reactions, or find out what is causing the behavior. Don't forget, nobody is perfect and if this were a human member of your family, you would try to work it out.