Best wishes to you with your challenge. No experience here.

The first thing is to make sure the diagnosis is correct. The person making the diagnosis should have experience with children or adolescents (whatever the age/stage of the person in question is); enough that they can differentiate the differences between hypomania or mania, and other causes for apparently oppositional behavior.

This is a page address from the facts for family online pamphlet about oppositional defiant disorder. There is a whole series of them on different mental health topics and children (and adolescents). There is a link on this page, at the bottom, to the 'main menu' of the facts for families (that link goes to a page with links to all the brochures).

http://www.aacap.org/publications/factsfam/72.htm

Children are difficult to diagnose because the symptoms of a lot of disorder types can look like oppositional defiance disorder. Also, having oppositional defiant behavior is a risk factor for all kinds of problems in a now and later kind of way. Try to find a counselor who has experience with children who have oppositional behavior. It's kind of like a double specialty area because the person has to have experience and expertise to be able to work with children; and they also have to have experience and expertise with oppositional defiance disorder thinking and resulting behavior-- and how to work with the child, and child's family in order to get stable positive modification.

Get counseling for yourself, this will help you with support and give you a place to get advice and support. Do not panic. There are ways to modify behavior which are known to work and which are not violent. You can learn how to support and enable your child to change by learning (and getting some psych support) how to establish a workable home routine-- with an understood and available set of stable rules and results for transgressions.

Even if I did have experience with one particular child who had oppositional defiance disorder, I still tend to think that people are individual enough that 'solutions' for one person won't necessarily work for all. Brain function is very complex. One generalizable thing about children in general is that they tend to (unless there are underlying problems) respond predictably to a predictable (to them) environment. Stability, and predictability in the home and from caregivers and adults usually helps them to be more predictable (to the caregivers and adults).

Make sure to get counseling support for yourself (as well as for behavior help for your child) because oppositional defiance disorder is a lot like antisocial personality disorder in effect. Most people, most of the time can't even imagine how a child could act 'that way' when they display this sort of disordered behavior. It's even worse if they are bullying because there can be victimization of others. It's a really rough road to travel to parent someone who has this kind of behavior disorder. A lot of people do blame parents, or home environments for creating brain-disordered behavior. This is complicated by the fact that these kids look as normal as any other kids.

anyway you will likely need some extra social support and probably having a counselor for psych support would also be good (family counseling is also a good idea if a goal of any 'treatment' is to create a changed pattern of behavior in one family member-- whole family involvement with counseling can really help create a stable new pattern)

Parent management training seemed to come up a lot with the subject of oppositional defiance disorder. Make sure you find a counselor who can direct you, and help you to learn any and all specific parenting tequeniques which have been proved to be effective.

This page mentions it, and offers a good explanation of how it works to help.

http://www.emedicine.com/PED/topic2791.htm

a child who has disordered behavior is likely to need something other than 'normal' parenting techniques

P.S. That page also mentions some other kinds of problems that often co-occur with ODD, and so are worth getting screened for so that they too can be managed.

I wanted to add, I thought my 8 y.o. son had ODD. It turns out he has Sensory Integration Dysfunction. He was so oppositional about certain things because he couldn't understand them. I want to second the above post that you make sure it's only ODD and not other disorders.

Good luck!