Setting my Preschooler straight

When my son turned 3, he came to a stage wherein he loved to test boundaries. Just like any kid, his favorite word became “No” and the more you asked him stop, the more finds pleasure in repeating the same offense. As a first time mom, it was very frustrating and tiring to be always arguing with him. I’ve tried timeouts but this did not work because after minutes of standing still in a corner, he goes back to his old ways as if nothing happened. At one point I became guilty of constantly shouting at him but of course this is not effective because what was instilled in him is fear and not realization of what he did wrong. Spanking for worse offense also became a source of discipline but I personally do not believe in this because most of his worse acts involve hurting himself and others such as his grandmother or yaya. Physical pain to stop him from inflicting pain is not a very logical idea.
After all the trial and error we finally came up with something that matches his personality; and that is privilege deprivation. For every wrongdoing, I give him a warning and tell him from the start of what it will cost him if he repeats the offense such us reduced time to watch TV, not being allowed to play with his favorite toy for a day or limiting his computer usage during weekends. This method worked for him because by depriving him of something he enjoys, the impact of his disobedience became more of a personal experience. He realized that actions do have consequences. I’m a working mom, so for this method to work, I have to involve his yaya and grandmother (Mama), whom he spends most of his waking hours with. Within my son’s earshot, I talk to Yaya and Mama that he is not allowed, say, to watch TV in the afternoon because he did not pack away his toys. By letting him hear my instructions, he is aware that even though I am not at home, his punishment still applies and I will know if it was followed or not. This improved our relationship because it saved me from getting angry or getting stressed while imbibing in him the lesson that I want him to learn.
As each child is different, so does the discipline method that works for them. What works for my son may not work well with others. How about you fellow mom, what’s the discipline method that works for your kids? I would love to hear your thoughts.