You need to be firm with your dog when it comes to giving your dog commands. Everything needs to be on your terms. A dog will try to run your household and take over if they sense a lack of leadership or weakness on your part. You must be firm!!!!!!
Your dog will require plenty of exercise and running to keep it happy and under control. Allow for it plenty of room to run with either a large field or back yard. If you do not, your dog will have a lot of built up energy and frustration which it may take out by chewing on furniture or being distructive.
Take your dog for walks on a daily basis if you can. This is important as it will provide for more exercise and training for your pet. Dogs such as Boxers or Greyhounds are high energy dogs and exercise will drain their energy levels and keep them at bay. Most dogs will get the physical stimulation they need from a brisk walk around the neighborhood on a daily basis.
Allow your dog a comfortable and secure place to sleep and eat it's food at. Your dog needs a den like sleep area that it feels safe in. You should also feed it there as well. This will give your dog a sense of it's own home it can go to and it will help you discipline your dog in some instances.
Constantly show your pet affection and nurture. Use positive reinforcement with your dog on a constant basis. Dogs love to make their owner happy and likewise you should show your boxer how much it means to you. They aren't called "Man's best friend" for no reason.
Lastly you should make everything routine with your boxer. Dogs in general like structure and their owner giving them a set time frame for everything. Take your dog out for bathroom breaks at the same time, feed it around the same time, and take them for walks around the same time on a daily basis. This helps build a set routine and it shows your dog that you are the dominant pack leader in your home.
If you follow these tips your dog will greatly appreciate you and reward you with a loving companion on average, about 6 to 19 years. Good Luck