My son is ODD, as well as ADD and Bipolar. We have known he was “different” since he was three, but over the years have gradually come to know how different. He is 14 now and so far (knock on wood) never been arrested, but he has had to be hospitalized a number of times for attempting suicide and for out-of-control aggression.
I find that Tenex (aka Guanfacine) helps lessen the amount of anger he seems to feel and reduces agitation. It may not work the same for everyone, but we can see him visibly relaxing within 15 minutes of taking it.
Exercise that he likes helps (in our case bicycling, baseball, and SCUBA). It should be a mix of organized sports so he can work on social skills, and free form exercising, such as cycling, so he can go as hard or as easy as he wants. Also, adrenalin-fueled sports will sometimes give an ODD child the “kick” they would otherwise get from anger, so they learn more productive ways to feel good.
A regular sleep cycle is absolutely essential because no one functions at their best without the right amount of sleep. It is just so much more obvious with someone who is ODD. Often Seroquel is prescribed because it makes people sleepy and so can help him go to sleep when he should. My son takes 800 mgs at night which will get him to go to sleep in about 30 minutes if we can get him to lie still. He also needs the Seroquel because when he is going into his manic phase he tends to hallucinate.
Therapy with the right therapist helps. This is not just for the child but also for you. It can be a lonely struggle living with someone who is ODD, and it is great to be able to kvetch to someone who can also help you map out better or just different strategies.
Also, learn to pick your battles. Some things matter a lot more than others. If your child wants to wear mismatched socks, so what? But if your child wants to break something, especially if it isn’t theirs, or hurt someone then that is a battle to fight. You need to learn how to hide your “buttons” so they can’t be pushed – ODD kids love to argue (my son says it “feels good” to be angry) and will grab every chance they can.
Learn how to be very, very consistent with rewards and consequences helps a huge amount. If need be write it all down, make charts or schedules and lists of rewards and consequences. In addition, try to keep clutter to a minimum so there are fewer distractions. In essence, create a “residential treatment center” at home.
And as @YARNLADY suggests, a support group can be a boon, whether online or in person.
Good luck!