Salary negotiation is not an easy conversation for both parties, and both parties should be well prepared for it. There are rules to take into consideration before discussing salary with a successful candidate.
Remember that salary negotiation should be a win-to-win conversation. Both, you and a candidate should be satisfied with its result. Otherwise, you risk either to lose a potential employee, or lose confidence in your leadership and communication skills.
Study a candidate's professional history and be well aware of how much he / she used to earn at previous jobs and what positions he / she used to occupy. As every candidate provides references form former jobs, you can contact referees and talk to them directly.
Although there are no rules what maximum and what minimum salary can be proposed to an employee, you should set approximate limits by yourself. This can be assumed from how many people in similar positions earn in your company and from current economic situation.
There are cases when a salary can not be negotiated. In order to attract an outstanding employee you can negotiate diverse financial and non-financial benefits, from paid mobile phone and covering tuition expenses to using a company car.
Even though you can be assured that hiring this person will make your company flourish, don't satisfy a candidate's excessive demands. Every company has got its own limits not to pass, and there is a point in it. If you decide to break the rules for one individual, no one guarantees you will not regret it.
If salary for this position can not be negotiated, inform the candidate about it in the very beginning.