Reprimanding your cat
If you need to reprimand your cat for problematic behavior (like scratching furniture or walking on the dinner table), you'll have to think like a cat to get results. You'll get no response from your cat if you reprimand him for something he did hours ago. Also, cats are social animals, and briefly "shunning" or isolating your cat from the rest of the household will get better results than yelling. A cat should never be reprimanded physically with swatting or hitting. Not only do they not understand this type of reprimand, it can quickly break the bond of trust and lead to even more bad behavior.
To get the best results, you'll need to catch him in the act and try to demonstrate the correct behavior. With problem scratching, move him to his scratching post and praise him indulgently when he uses the post instead of the sofa. This associates positive reinforcement with positive behavior. You may also want to place them in a safe, closed room or their cat carrier for 5-10 minutes, away from toys and family members, to get your point across.
It is possible that certain types of persistent bad behavior could also be signs of health problems. For instance, urinating away from the litter box may be an indication of a urinary tract infection. If you're not sure whether his behavior is just a bad habit that needs correcting, or something more serious, contact your vet immediately.