The goal should be to find a salary that is appropriate for the employees skills and experience level. Neither too high nor too low.
You do not want anyone to "win" the negotiation.
The idea is to find a salary that will ensure that the employee feels that they are being appropriately paid during their employment, and will not be browsing jobs because they feel they are under market rate. You want to employer to feel that they have someone who is being paid at a level that reflects the employees skills and experience and is broadly consistent with other employees at a similar level.
Negotiating isn't a battle. It's a process of trying to find if there is common ground.
If the employee and the employer do not find satisfactory common ground then the negotiation should end gracefully - both parties move on.
It's important to work out at the very beginning of the employment process if jobseeker and employee are in the same ballpark on salary - it's silly and wasteful of everyones resources to get to the end of a process only to find out the parties expectations do not synch.