I don't know. I'm not a big fan of spanking but what else can you do? It's not like your kid has any sort of understanding between right or wrong. You have to teach that to him/her.
How do you do that? There isn't really a set way. I mean, I got beat as a kid and I'm perfectly fine today. My parents didn't "fail as parents," because of that.
I don't know where you expect to get with sitting a kid down and talking to them. I mean, they are kids after all. Just don't spoil your kids. Tell them no, make sure they understand at a young age that they can't have whatever they want. Then go from there.
I'm speaking from my personal experience really. My grandmother, when she raised me, talked things out with me. She explained to me why things were wrong before she ever resorted to hitting, and I responded far better to talking simply because when I got hit, it just built up negative feelings.
My father hit me, and it ruined our relationship, I never liked being around my dad and loved when he left for trips overseas because of his job or whatever. Not because it meant "I can do whatever I want now, I won't be hit", but because something inflicting any type of pain on me is something I naturally sought to avoid. Getting hit/spanked/whatever for things didn't make me think "Oh I'm going to stop doing it", it just made me want to find ways to not get caught. Like you said, kids aren't gonna be so keen to reasoning, not every kid is gonna say "That got me hit, I don' wanna get hit, I'm gonna stop doing it", but probably say "I just don't wanna get hit." Sometimes, spanking doesn't get across "What you did was wrong". That's why I personally find it better to sit your kid down and explain why what they did was wrong, and what they should do instead. I once got caught playing with matches, and my instead of spanking or hitting, my mom just explained to me flat out I could burned the house down and killed everyone inside, so I avoided playing with matches.
I've seen other kids who got spanked and just felt some sort of negative feeling towards who spanked them, and then when the feeling went away(they're kids after all), and then continue doing it by try harder not to be caught because they weren't actually told "This is wrong", they didn't fully understand that part.