'No' is the ultimate negative command and should be used carefully when working with babies and young children. Although baby's recognise 'No' from around 6 months, they may not actually react and stop what they are doing until somewhat older as they approach a year. It's very easy to scream 'No' at our little ones the whole time, every time that we see them doing something that they shouldn't be doing, and especially as they start cruising and exploring the house in new ways.
Try to balance the negativity of 'no' with some positives and you will reap the rewards - you will find that your little ones become far more responsive. Instead of yelling 'No', explain why you are saying it. Perhaps use 'Hot' if you mean 'No, don't touch, that's hot!', or 'Bang' if you mean 'Don't pull that, it will fall!' and so on.
Instead of leaving a negative taste in their mouths, explain what your little ones CAN do. Demonstrate that they aren't to play with a small-easy-to-choke-on-object, instead give them something that they CAN play with. Rather than telling them 'No' when they start pressing buttons on the television, give them something that they CAN press buttons on, like a keyboard on a computer that is turned off or a remote controller with the batteries removed.
Balance 'No' with praise for positive things. When you observe your little one doing something good or safe, reward them and tell them they are doing well. This will discourage them from doing bad things simply to gain attention from you.