First n foremost educate yourself and him the more you know the better able you will be to help him and yourself. Love him no matter what. learn to seperate him from the disease. n yes it is a disease. it is not him. he can not always control what he does or says or how he reacts. or how he feels. always be open to what he says even if it hurts he will lash out at those he is closest to. It sometimes seems that they can hold it all in when they are around everybody else but the minute they get home .....BAM.....they let it go.....At least with my son. know your drs. know your meds don't hid anything about the illness from your son. be up front with him the more he knows the better off he'll be the better able to cope he'll be. you don't say how old he is. My son is now almost 16. Believe I have lived it! ALL OF IT! He's been bi-polar since birth. diagnosed at age 4.5. no meds til age 8.
Love him. Support him. Give him information if he wants it. Go to therapy with him if he wants it. Let him know you'll always be there for him no matter what. See the good in him. Point out the positives. Don't ever make him feel "crazy".