When it comes to negotiating, sports agents are some of the best in the game.

They help their pro athlete clients get multimillion-dollar salaries and specific terms in their contracts -- all without having to break a sweat.

Who better to turn to for advice on how to negotiate a raise or promotion than a longtime sports agent like Phil de Picciotto?

He's the founder and president of Octagon, a sports and entertainment agency that reps athletes like Olympic gold medalist Michael Phelps, NBA champion Steph Curry and NFL Hall of Famer Emmitt Smith.

De Picciotto sat down with CNNMoney to share his best tips for acing a negotiation.

Be prepared

De Picciotto said it's important to go to the meeting with hard data, such as information about the company's growth or figures that show your performance.

"Know your facts and don't only know them from your side, also know them from the other side so that you can anticipate and there are no surprises," de Picciotto said.

You'll be more confident if you enter the meeting with facts -- they're harder to dispute.

Just make sure your points are solid, de Picciotto said the last thing you want to do in any negotiation is make it seem like you're bluffing.

Choose a style or tone

It's crucial to be yourself, but it's also important to decide how you want to act while you present your pitch. Do you want to be firm or nice, serious or upbeat? You should also consider your body language and level of emotion.

De Picciotto said any style works as long as you're comfortable, genuine and professional. He said it's also important to make eye contact, stay calm and be respectful.

"It's very important how one acts, probably more than what one says because negotiations are so personal," he said.

De Picciotto said he wouldn't advise getting angry but that it's certainly okay to be passionate. It's even okay to shed a tear -- to a point.

"If you never cry in the workplace and all of a sudden something is said in a meeting and you start to cry a little bit ... that's an element of surprise."

He said the act could be enough to make the other side realize how serious you are about your proposal and give it more weight.

Get your story straight

It's always a good idea to practice what you're going to say beforehand. That way when the time comes, you have a clear understanding of what you're asking for and how.

Be specific about what you want versus speaking in generalities or abstract concepts.

For example, if you've done your research and can come up with an exact dollar figure or percentage for a raise, that's a better approach than just saying you want to be paid more.

Don't make it about you

"Start with the company ... and always bring it back to the company," de Picciotto said.

"I would always try to lead what value you can give to the other side. Going in and saying 'I want' sounds like a demand."

De Picciotto said demanding things or being too aggressive "will put the other side on a more defensive posture. It's not very collaborative, and it won't usually yield the results that you want."

He also said that in an ideal situation, the negotiation meeting "should never be the first time you speak to somebody."

Be prepared to walk away

"It's an acceptable outcome if staying is not going to make you happy," de Picciotto said.

"In this current generation there are more job opportunities, there's more mobility, companies are changing much more rapidly, and having multiple jobs in your career is ... quite commonplace."

Still de Picciotto suggests asking why you're being turned down before making any immediate decisions.