At the Termination Meeting Listen, Ask Only Pertinent Questions, and be Professional
The severance agreement is generally delivered to the employee at the termination meeting. This is a meeting that the Employer has arranged and prepared for, and that the employee may very well not be expecting/ not expecting it at that moment. Also the Employer may have 2 or more people present on its behalf for this meeting (for support and as witnesses), while the Employee will be all alone.
At this meeting you should mainly be listening, and keep your talking to a minimum. If there are pertinent questions that you have you may want to ask those questions, but it will probably not serve you well to ask too many questions or be confrontational. During this meeting the Employer may very well say claimed facts and detail its claimed reason why it made the decision to terminate your employment - claimed facts and reasoning that you/ your attorney may later be able to use as admissions as well as show are faulty/ disparately applied. But if you are not listening closely (and subsequently writing detailed notes about what was said) then whatever the Employer said that may otherwise be useful for you will be lost.
Remember, anything you say at this termination meeting can and probably will be used against you either as a claimed admission or to disparage your character. The Employer has already made its decision to terminate your employment, and few if any Employers are going to change their decision. While there may be a certain satisfaction to speaking up and telling off the Employer/ telling the Employer what you really think of him/ her, from a tactical and negotiating standpoint that is not helpful - and may very well reduce/ eliminate any opportunity for you to later obtain more severance. Likewise, yelling, screaming, and threatening is not helpful, and (although in a movie it may make for an entertaining scene) this may undermine your cause: instead just be professional.
Also keep in mind that at the termination meeting (and thereafter) if you try on your own (without an attorney) to negotiate more severance - and the Employer says no - then this will likely make it more difficult for your attorney to later successfully negotiate more severance for you. So think long and hard before you speak.