Start off by removing the idea that you need to be demanding or rude to get what you want.
This idea is counteractive to what you want and humans know how to combat anger. Think of what you want is like a bullet wound. Your expectation is to apply pressure and do everything required to close the hole and allow time to heal while not bleeding out due to the lack of attn.
Let's Start with the basics.Be Friendly and Respectable. Being friendly is expected to first earn the respect of the person you are looking to get what you want from , Don't be multiplicative or deceptive. Be clear on what you want. Be Stern, Constant. Apply friendly pressure but keep the pressure constant. Don't lean back or give up. there will be a large group of people trained to tell you NO, or you cant. Or that is now how things work, avoid them.
Apply Pressure anyways. This one is huge. "Apply Pressure" You have herd this all your life. "Early Bird gets the worm", "Squeaky Wheel Gets the grease" You all have heard this before however many have mistaken that in order for this to work you have to be in a complaint format or a problem format. This simply is not the case. Know what it is you are after. Lets say this. You are looking for a refund from that store that just burned you. They claim you must wait a month for the process to get your money back. They tell you there is no other way but to wait. Well here's the thing about that, You are human, They are human too.
If there is no fire there is no fire truck. and if there is no fire truck there is no problem to solve. So when they say you will have to wait. Then your response depending on the format is pressure biased. your waiting in the store "You will have to wait for your refund" your reply is "OK i'll stand right here at the desk" It is not your job to worry about the people in line behind you. If the medium is phone. "The refund will take some time, You'll have to call back to check on it" your response "Thanks but i'll wait while you look into it" Remain friendly and helpful with a non combative resolve. you know you want a refund.
So apply pressure. Keep it constant. The pressure needs not be a sharp pain but a minor discomfort. Don't get ahead of yourself. This is only effective as the moderation you apply to it. Becoming overbearing or too power struck will have a bad effect. The goal is to encourage empathy not belligerency. Doubt yourself often and user your own logic as moderation. Will this method work in this fashion? Should i change my tacit? You must know there is no one way to unilaterally solve issues. Think for yourself. My words spoken here are a uniform for you to hear with a small grain of salt. They have no real value other then an affirmation of my own values.
It is up to you to take what I say and translate it into what you believe is right. Be a good person. Do the right thing. Apply pressure and it won't matter what others say about you. At the end of the day those who know you and know your true values, They know you get things done, they know you always get what you want. And you Always are an asset to the right cause.