Be confident
According to the Harvard Business Review, you must start by believing in yourself and your skills. It is no use convincing anybody about these skills if you yourself are not confident. You personally must feel that you are entitled to what you are about to ask for.
Remind yourself of the asset you have been to the company
Make an analysis of everything you have brought to the company while working for it. Point out the projects with which you succeeded and the systemic changes you initiated.
Interconnect your request with the aims of the company
Every company has its vision and direction. For the request to appeal to your boss, it must be in accordance with the direction in which the company as a whole is moving.
Have a clear idea
Do not go to your superior with just a vague idea about a non-specific change that should be made. Come with a specific request that you can support with concrete arguments.
Prepare your monologue in advance
While it might seem stupid to you at the beginning, it is worth practising your speech in front of a mirror. Or you should at least say it to yourself in your own words. That way you might detect any weak points in your request.
-mm-