Basic Classical Conditioning
Temperament problems occur when a dog is feeling upset, uneasy, anxious, or possibly terrified.
If your dog behaves in a fearful manner, or if they behave aggressively, but they have good bite inhibition, then their temperament problems may be alleviated and eventually resolved, but it is vital that you start resolving them immediately, starting with classical conditioning.
The classical conditioning concept is very simple. Expose your dog to whatever stimulus is triggering their anxiety immediately followed by a stimulus that they enjoy.
When the trigger stimulus goes away, so does the pleasant stimulus. When the trigger stimulus comes back, so does the pleasant stimulus. Repeat this procedure over and over and your dog will begin to associate the trigger stimulus with the pleasant stimulus and they'll start to feel better about the trigger and eventually, learn to not only tolerate but to thoroughly enjoy the trigger stimulus. At which point you have disarmed the trigger.
The easiest, most convenient and most reliable pleasant stimulus you can use is food. Food is especially effective if you do not feed your dog outside of training. If your dog has access to food elsewhere, they may feel indifferent to food, especially if anxious, and the food will lose its potency as a pleasant stimulus for classical conditioning.
That said, you, your voice and your mood are also really powerful therapeutic rewards. If you don't mind acting silly, doing little dances, singing little songs, playing with and praising your dog in a sugary sweet voice, you can achieve a lot of classical conditioning simply using your own behavior. Now, not everyone is willing, or capable of acting so obviously happy, which is why food is mandatory for classical conditioning, especially if your dog is anxious about people.