Our sense of morality is usually deeply internalized. We know right from wrong most of the time without needing to stop to think about it. There is a naturally automatic aspect to morality, for most of us.
If a person were deliberately amoral, he would be choosing to undo his internal morality and, beyond that, choosing to replace it with a code of conduct that has nothing to do with morality or right and wrong.
To be deliberately amoral means that a person is consciously choosing to remove himself from questions and judgements of right and wrong. We might usually interpret this as a choice to do "wrong" or to become "evil", but there is some grey area.
Most simply stated, a deliberately amoral person refuses to use right and wrong as guides to behavior.