At some time or another even sweetest cat "misbehaves." Ironically, a cat's bad act is usually quite normal behavior for her, but may have a result humans don't like or want. Screaming at cat or physically punishing her won't alter negative behavior. The best way to change undesirable behavior is to eliminate opportunity and/or distract cat to an acceptable alternative.
Immediacy is vital: even seconds late may be ineffective. You must do it as soon as cat starts misbehaving.
Distracting a cat away from an act is not very difficult. A loud, unfamiliar noise will quickly get her attention. Some cat owners use a low growling sound, others imitate grating sound of a game show buzzer. Keeping sound low-toned and harsh is important, because you want to save high-pitched sounds for praise and reinforcement of positive behaviors.
One well-known way to distract a misbehaving cat is to give her a blast with a spray bottle. While this works, it has some drawbacks. First, you must have bottle in your hand at exact moment cat is about to act in a way you want to discourage. Unless you follow your cat around all day with a spray bottle in your hand, this is unlikely to happen. The second problem is that this technique seems to lose effectiveness after a while with some cats.
The best way to extinguish negative behaviors is to remove opportunity. If your cat obsessively scratches side of your couch, place a loose blanket or hard acrylic panel against it. Both techniques remove her access to satisfying feel of fabric. If she climbs your curtains, shredding them as she goes, fold or pin them out of her reach unless you are around to stop her. If she has accidents only when you are not home, only give her free run of house when you are there. When you go out, close her in a room with food, water, litter box, scratching post and a couple of toys.