I rarely just say 'no' and expect them to understand exactly what I mean by that, because 'no' is not enough, though I was brought up to believe it was. It isn't respectful, IMO - I'd hate it if I was doing something and another person told me 'no' with nothing else in it.
I agree but there are times when it wouldn't need the over thinking/explaining. Here are a few example of what I meant with the over explainin/thinking.

Can I have ice-cream? It's nearly dinner time so no not until after dinner. Continue to ask for it and it get's counted - no further explanation needed - get to 3 and it's time out (or in for us with us)
Hit your brother/sister other serious behaviours are 3 straight away with time out/in.
Iz can you clean up your toys please? Doesn't get done for whatever reason - get's counted, so she gets a few chances to do it before time out.... It's not about giving them time to keep doing the bad behaviour - it actually reiterates that we have asked reasonably for something to be done and if it doesn't get done there will be a consequence. For DD being 4.5 - there is no need to over explain WHY we need her toys picked up, she knows it's messy, needs to be done prior to dinner. Not sure if that makes sense.

Naenae - Not sure if that make sense but as for the 123 - it gives them time to correct the behaviour or whining, but if the behaviour is serious then it's 3 right away.