More about training
Of course, even using remote punishment like the water-pistol will only probably train the cat not to do whatever it is - e.g. jumping on the kitchen counter - when you are around. Some people have had good results with completely covering the counter with pots, pans and utensils so that the cat is bound to knock something over when he jumps up, and give himself a fright. You may of course feel that this is really too much trouble and makes the place look untidy. An important thing is that the cat should NEVER get a reward for jumping up there, so don't EVER leave food out there. If the cat never finds any chicken or other tasty morsel there, he will probably not continue jumping up, but if he finds something nice even once, he will keep on trying.
Using a powerful cat-repellent can be effective in stopping your cat from scratching walls or furniture, and of course you must provide a scratching-post. Spray the post with catnip to encourage your cat to use it. If he is reluctant, every time he scratches something else, take him immediately to the scratching post and put his front paws on it, and imitate the scratching movement. Most cats do get the idea.
Let me know what YOU think!