Raising your adopted child can be a rather difficult and challenging task. There may be psychological and emotional impacts which are hard to handle by the child as well as you. Children may react in an adverse way if they come to know suddenly that you are not their biological parents. It is wise to tell them when they are old enough to understand. But it is never the right time as they are going to get an emotional jolt.
The most difficult period is when you are dealing them during their adolescence. They will hate you as they know that you are not their actual parents. Hence they will refuse to obey your orders or even if you scold them they will turn a deaf ear. They can make life pretty miserable for you but do not lose temper. Only love and patience can help you win your child back and they will realize how much you love them irrespective of the fact that they are not your own children.
If you plan to adopt a child of a different race you are bound to receive weird comments from people. Try to face it and teach your child to face it too. Tell them that he/she is your child and you love them because that is all what they want to know.