Negotiating a good deal is an art. But you need to know your priorities first, and what actually makes a deal good before you start. So before you begin, rate each negotiable item on a scale of 10 so that you know what matters to you. Something that matters a lot to you, like non-negotiable leave during the holidays, would be a 10. Something you don't care about, like remote working, would be a one. If either of those matter more or less, rate them in between.
It's best to do this for your own reference. No sense in showing your cards unnecessarily, so don't come in and say "leave is a 10 on my list" to your potential boss. That said, John Rampton of Inc. says he even opens up the rating at times a little.
Want to know how strongly you or your counterpart wants something? Put a number on it. A number 1, for example is neutral, and 10 would be something you can't live without. Hopefully this will lead to both parties eventually comprising or coming up with an alternative. This has allowed me in the past to be very direct with the other party in letting them know what I'm not willing to leave on the table.
Read Rampton's full article for other tips to negotiate any deal, like labelling emotions to drive a point home.