Smacking is lazy parenting IMO.
I was smacked and My feelings towards my parents were rather negative. I was a good kid but although I loved my parents I also resented them, slightly feared them and found them unapproachable.
I have 3 children, all well behaved, polite and happy. I am quite a strict parent with zero tolerance for back chat and bad manners, and a short threshold for nonsense. I do not smack my children!
Those who want an ultimate solution to bad behaviour or a direct alternative to smacking, will be waiting a long time for an answer because there isn't such a thing. Every situation and example of unwanted behaviour needs dealing with in a way that is relevant to the problem at the time.
The main thing is to have your children's respect. This is earned by making boundaries clear, being consistent with your expectations of them. Making consequences clear and following through with any threats - always.
When your children respect you, they care about how you feel. They want to earn your approval and get disappointed in themselves if they disappoint you.
Teach them good behaviour by example, give them your time and attention, positive praise is a huge deal, as a motivator and an esteem builder.