Most dogs will howl when they're seeking attention from you or someone else so if the dog is howling because they're seeking attention from you then you or anyone else should ignore the dog when it's howling for attention.
As soon as the dog starts howling do not look at him/her and immediately look away when he/she does start to howl.
If the dog is howling because you're leaving it alone in the house while you're gone then you can give them a sensory toy to play with or leave a radio on so they don't feel alone.
You can also use shock collars on the dog that you can activate when the dog starts to howl when they shouldn't.
The dog will eventually learn to not howl when they shouldn't be howling.