I remember asking myself that same question and not getting an adequate answer. ODD can be very difficult to manage, and harder still to understand.
I learned that my son's ODD was worse when he was hungry and tired. To this day, if he has an episode, I deflect the tirade and feed him. When he is tired, I do my best to ignore the words (not easy at times, as they can be very hurtful,) feed him, and put him to bed. I found that low blood sugar and lack of sleep are two major culprits for bringing on an episode.
Something you need to keep in mind is, your child is growing and changing daily. What worked one day may not work the next, and vice versa.
I found that different techniques worked at different stages of development.
The hardest thing to do amidst all the change and behaviours is to be consistent. Reward the little things - when your child surprises you with good behavior - make sure you recognize the achievement - I know sometimes they are few and far between. There were a few years that I thought I would never be able to make a difference - that my son's behaviour would never improve. I tried everything I was told in the hopes that something would help - a lot of trial and error.
I kept my son in counseling for many years (as a matter of fact, he still sees a counselor,) and I kept trying.
Some of the things I tried worked (a few times) and that gave me the strength to keep going. Unfortunately, there is not one single thing that is the magic answer. Learn everything you can about the disability - knowledge is power, knowledge is strength, and you need both to survive the ride!
You can contact me through HubPages - I might have a few solutions that you haven't tried yet that might help. Stay strong, and be kind to yourself...you aren't alone.