Hi & Welcome Sharon...
ODD is a hard one. I had a look into it a bit because my
DD is extremely defiant. Its apparently part of Autism which she has.
Our OT (Occupational Therapist) has helped us work on some of her emotional regulation issues and that has been good. The OT is teaching her how to physically force herself to calm down. We have taken the word "No" out of our vocabulary and now use alternatives. So instead of saying "No, you can't have the juice", I say "Matilda, you can have water or rice milk to drink". And simple things like that which have helped us avoid massive fights.
We also found diet to be huge. We have done the Failsafe diet and found certain preservatives and natural substances affect my daughter's behaviours. Now we can avoid those triggers by changing our diets. We went chemical and preservative free and started on a whole foods diet which was amazing. We found our daughter reacts severely to apple juice. She could have lemonaide, or cordial and not react as she does with apple juice.... so its good to find the trigger and be able to say "we'll have something else thanks"