As children near the age of two, they begin to exhibit a behavior called negativism. This behavior is easily recognized by a frequent "NO" in response to nearly every parental suggestion. Understandably, parents can become quite annoyed at this bewildering development in a child's life. Actually, this negative behavior is a normal part of a child's development, and it signals the transition from babyhood to childhood. (It is not unlike the behaviors and transitions of adolescence.) Your child is asserting herself - seeing how it feels to make decisions on her own. And part of making these decisions is disagreeing with her parents.
A child at this stage may appear defiant. He wants to do everything immediately and wants things done in the same way every time. He makes unreasonable demands of his parents and tries to dominate them. He says "no" even to things he wants to do. Through this process, the child is learning the distinction between his own will and the intentions and will of others, notably his parents. This rocky road is an important one that leads the young child to autonomy.
As aggravating as this behavior can be, remember that you are not the cause of your child's contradictory behavior. All children at this stage of development struggle to assert themselves, although there are individual differences in how this battle unfolds. It's important to accept that not only is this an inevitable stage of development, it's a very necessary one. And remember that sometimes your child may not really want her "no" to be taken seriously.
It's not hard to understand why saying "no" is so popular with young children. After all, they've been hearing their parents use this word with them for most of their young lives. One way to moderate the negativism that occurs at this stage is to reduce the number of times you use the word "no" with your child. Although it takes more energy than giving a firm "no" from across the room, it makes better "child development sense" to divert the child from the unacceptable activity. It is also wise to explain to him what you are doing and why you are doing it, even though he may be too young to understand.
Congratulations! Your stubborn and rebellious toddler now knows she is not a baby, but she is not sure exactly what will happen next. As her parent, you cannot be certain either. You may be experiencing some ambivalence about your child's newly acquired independence. Although it may be difficult to remember while your child is energetically emptying cupboards in your just-cleaned kitchen, try to keep an appreciation of her process of self-discovery. The beginning of this lifelong journey happens only once.