K.B.
My daughter is going throught the same thing, she is 4 1/2 now, the defiant behavior started a little before she turned 4 years old. It is getting better, after 6 plus months of repeating yourselves. I have to keep reminding myself to not get mad, repeat myself, do the consequence and repeat.
We always have consequenses for not listening, it depends when she does not listen.
--- Not picking up toys when told to, toys get taken away for a week (if it happens again two weeks).
--- Not eating dinner, no dessert.
--- Not walking/following rules for being in the mall/parking lot/store then you MUST hold mommy's hand even if you do not like it, till you do as mommy says. Have to show you can do something to earn the responsiblity to not always holding mommy's hand.
At times kids are being defiant to get your attention. I have found that if my daughter does something for example: throw/kick a toy when I walk into a room, it is to get my attention not just to be bad. So in the toy case I simple take it away, paying no attention to her. She usually runs after me either asking why I did that, which I reply 'you were not respecting that toy so I took it away, I will get it back in one week' OR she will say she is sorry and will not throw/kick it again.
I also arrange a time where we do something fun, just here and I, that she picks to do (with in reason like library, coloring, painting, playing trains, puzzle, game... once a month she can pick a place that costs money). I have found that once I started doing this daily she was less defiant because she got the attention, in a good way, from me so did not need to seek for attention with bad behavior. This dose not solve all the defiant behavior, but a lot of it, the rest of the time have to have consequenses that deal with that situation.
With our time outs my daughter has to stay in a time out till she says sorry for whatever she did, and what the proper behavior she should have done. Sometimes it takes a minute or two, other times it has taken 10-20 minites, depends on how defiant she is being. I NEVER give in and anything that is taken away is taken away for at least a week, to me anything less and the kid does not appericate what they have or they know that they will get it back in a day or two so they can wait and that defeats the whole point of what you are doing in the first place.