It is important to know your current and true worth whenever entering into any HR negotiation and discussion.
The way it works internationally - the HR usually receives a budget for a certain role they are interviewing for. For example, for a fresher role in an IT company, the HR comes in with a budget of 45-55k Euros. In most cases, depending on the skills and the negotiation leverage you bring to the interview, the HR will try to be as close to the 45k mark, while your goal will be to demonstrate your worth through your true value in the market and your experience, in order to reach as close to the 55k mark.
For this game (yes, this is a game) you need to be well aware of your true worth in the market - sometimes you shall even have to state your true worth in your negotiation - ex. X & Y company have already agreed to offer me 55k, but I prefer your company - so I expect you to match the offer.
So the primary question is - How to know my true worth?
For this, the following strategies can be implemented!
Ask people in other companies in the same sector, who occupy similar roles:
This is not always possible - in that case check with friends in other sectors but within the same experience years range. This will then need to be adjusted for the sector.
Check up websites for salary checks - Glassdoor or Kununu
Go through interviews and test out live
Ask a senior you know in any company in the same sector
With this information, you are in a position to enter the salary negotiation at any company!