A good book to read is 123 Magic: effective discipline for chidren 2-12 by Thomas Phelan. This book uses a very simple approach by using the 123 counting method for behavior. What is nice about the approach is that it is presented in very positive way and stresses not to engage in arguing with your child which we all know does not work and it puts the responsiblity on the child for their behavior.
I have a very strong-willed 4 year old who used to throw tantrums when he was two and I can't tell you how many times he banged on his door. (I wish I had thought to remove the door)
I chalked it up to terrible twos which I am sure that some of it was, but at 3 he began to argue, and at 4 he thinks he is the boss. Mom and Dad here are both strong-willed so I know where he gets it from and I guess he has a double dose lol. I have come to learn that this is his personality and he too can be so lovable and wonderful. I have found with him that I have to constantly change things for consequences to work. I used to take things away and that worked for a while, but then he did not care what he lost so we had to come up with something else like going to bed early.
I have done the 123 magic approach with him and it does seem to work - he will even remind me when I have already counted to 1 as he is keeping track. We have started him on an allowance thing also which seems to motivate him. Other things you can try are charts and stickers etc. as children like to see their progress and be working toward a goal. I think you have to try different things as what works for one child may not work for another. I also think you have to pick your battles with kids as some things are just not worth the argument. I have found using the 123 apporoach has helped to defuse some tantrums before they start but the key with this approach is consistency. Hope this helps and don't worry things will get better.