In order to identify your real needs and concerns, ask yourself: "Why do I want what I want?". You will then quickly realize that you have good reasons for wanting what you want.
A practical example.
What I want (position):
- I want to get a lower price!
Reasons why (your underlying interests):
- „The quoted price is doesn't make sense to me. It is important for me to understand how it was calculated.“
- „I'm under pressure and must increase the competitiveness of my company.“
- „The system they want us to buy has way too many functions. I just want to buy (and to pay for) what we really need.“
Do not take a position. Write down your underlying concerns, needs and interests, and explain them during the meeting.