ok, so what if they still do it? You just talk to them again? You don't have boundaries if your kids can cross them without any come-back.
So this is so situation dependent hard and fast rules are irrelevant. And the main thing is, in the absence of SEN, if you instigate communication and empathy as the basis of your discipline early doors you don't tend to find kids are ghastly for the sake of it.
Punishments/consequences/whatever you want to call them should be relevant to the crime. So if child throws a toy that isn't for throwing, and won't stop when told not to, you gets taken away. No need for a totally irrelevant punishment like a smack or a naughty step.
My daughter was being a mardy so and so at the playground just now (long day at school so tired); couldn't reset her with usual hug and deep breaths, so I took her home. She wasn't happy about it; but she wasn't happy anyway so hey ho. She's now had a veg out and a drink and she's sorted. No need to have a massive "discipline" moment. I'm sure I could have smacked her; but I don't think either of us would have felt better for it.
Stealing? Not one I've had to deal with yet. But I think I'd get the child involved in returning what was stolen and making a meaningful apology, and if they'd been able to do it due to trust bring extended that had been breached (allowed to wander round the shop for e.g) then in future that freedom would be withdrawn until I could trust them again (based on good behaviour and or articulation of their understanding of why it was wrong).
I mean when I have an older child I may have a different view - but by then time outs and naughty steps have pretty much ceased to be appropriate anyway, so if you haven't done the work on communication and self control you're a bit fucked anyway - unless you're going to up the ante with physical restraint. By that point, you really jeed to have established the kind of relationship/outlook that other people matter; doesn't mean they'll always be angels but means that "talking to them" still has relevance as you're speaking to values they already fundamentally subscribe to, lapses aside.
Little kids aren't usually naughty because they want to be; they have low impulse control and poor theory of mind. They need help to learn how to empathise with others, and not to be put in situations where there impulse control will be overwhelmed too easily.