Don’t hide the message. Be direct and begin with the reason: “I have bad news, you are being let go due to X”.
Make eye contact as you do this, and wait for the reaction. In this situation there is still an opportunity to build trust in each other, and communicate that each party will act properly. Most people react calmly; more often than not professional instinct takes over.
Once that is said, acknowledge the difficulty ahead, and put them at ease. Offer genuine help if you are in the position to give it. “I know this isn’t what you want to hear, but I am going to do my absolute best to make this as smooth as possible”.
All the salary, compensation and notice period calculations should be performed ahead of time, and you need to immediately summarise these. On recieving this news most people feel immediately threatened and need the reassurance they are going to be treated fairly. “You will be paid in full for your notice period of £X, and your holiday allowance which is £Y”. Stick to the dates outlined in the calculations. If there is any disputes at this point over money owed or compensation due, defuse it and accept there may have been a mistake (very rarely does this actually happen). Just say “we will look into any other money owed and make it 100% right with you before you leave”. This conversation is not about money but sometimes its easier to vent anger or shock by pretending that it is.
In general, most people move very quickly go into planning mode. I usually offer unlimited time away to attend interviews, and offer use of any company facilities and equipment to help them search. Equally some people don’t want to attend the office at all.
I usually finish by asking about messaging. I try to give the employee control over the story to their colleagues. Some may be embarrassed, especially if this action is being taken due to performance or conduct reasons. Give the person time to think about this. There is usually zero impact to the company for someone to say “I decided to look for something new” rather than “I was fired”, so unless you have very good reason, you don’t need to control the narrative.
Finally, offer a further meeting very quickly, such as lunch the next day. This offers them a chance to speak again about their feelings once they have processed them.
Remember at all times that we need to be human, decent and honest to each other and sometimes the best thing you can do is quietly listen.