Billybookers has some great points. Rewards for good behavior is the best. How you deal with bad behavior is a bit different.
I'm fortunate, Tulsa doesn't want me out of her sight, so I can confine her and walk away. When I come back to her, she's eager to please, and has the intelligence to put it together.
As I said in another thread, she was leash aggresive, didn't like men, or children, would lunge and snap when on leash.
It took daily sessions that lasted several months to get her over these issues.
It doesn't happen in a day!
That's why we have so many dogs with GREAT potential in our shelters.
People with no knowledge of dogs expect them to be good dogs in a day.
It takes a lifetime of positive training to turn a dog into a companion.
It may look like 'work', but "Love" is another four letter word.
John