Understanding how the factors of Right Livelihood come about, we have to look at the Noble Eightfold Path. It begins with Right View, basically understanding the Law of Cause and Effect, that everything that we think, say and do has a result, understanding the Law of Kamma and the Four Noble Truths. Right Intention, thoughts directed towards harmlessness, free from ill will and cruelty. Right Speech, Right Action and Right Livelihood. In order to know whether our livelihood is Right Livelihood we have to see whether it is based in Right View and Right Intention. And whether in our livelihood we have the opportunity to do Right Speech or wrong speech. Right Action or wrong action.
Right Livelihood has to be supported by the other factors that come before it to enable it to be Right Livelihood for ourselves. So, in our livelihood, are we doing livelihood that brings forth beneficial results for ourselves and others? Is it not causing harm to ourselves and others? This is Right Intention. Is it enabling you to do Right Speech or do you have to engage in wrong speech, is it untruthful speech, etc.? Right Action, action that doesn't cause harm to ourselves and others, doesn't exploit others in any way. So in order to know whether we have Right Livelihood, it has to be supported by the other factors of the Noble Eightfold Path before it.
Right Livelihood will be different for different people with different aspirations. So investigate into these factors to see whether it is Right Livelihood for you, does it bring forth opportunities to make Right Speech and Right Action, help ourselves and others or not harm ourselves or others? For example, a situation where one is a secretary, normally there is no problems in this, however if this person does computer work in a tobacco factory or firm, it would be difficult to say that a tobacco factory is useful for the world. This includes seeing the actions we do and whether they support harm in the world or not.
Doing computer work for an ammunitions factory may not be Right Livelihood, if we look at it deeply, because the company is making products that can cause much harm. So, it may be a simple action where we are not harming people directly, but if we are supporting a manipulation or exploitation in the world then it is not Right Livelihood for ourselves - if we are truthful towards ourselves. Whereas if we are doing computer work for a school or a hospital, we may be doing the same sort of mundane things, but we are not supporting an institution that is causing harm, but rather is helping people. So these are some of the factors that we look at in order to know whether we have Right Livelihood.