Effective discipline strategies for a 3 year old?

My son just turned 3 last month and he doesn't listen to my no's a lot of the time. I try placing him on the step for time out and he's worse when he comes back. He's mostly good, but then he has moments where he hits and throws things at us. I try to tell him calmly "we don't throw things like this at people, it hurts". But he does it again. Or when he is being defiant and I tell him "no, we don't do that. We do this instead." He still chooses to do the bad thing. I always give him praise when he listens, however ill admit that I dont have effective discipline strategies. His father doesn't help since he feels guilty if my son starts crying while I'm disciplining him. He doesn't wsnt much TV at all and we are actually outside most of the day.

I will say that I do not spank him for bad behaviour and don't want to. I also prefer methods that would make him want to do the right thing, rather than punishing him.

Any tips? Thanks!