2. Have multiple offers. At least two if you want to have any leverage at all. "I want X" is vastly less effective than "I have another offer for Y, can you offer more". Guessing that you're being low-balled possible, I guess, but it's much safer and easier to actually auction your work. Bluffing might work but having a strong BATNA is way better.
[1]: https://www.kalzumeus.com/2012/01/23/salary-negotiation/
Maybe check this out also for better awareness of HR "power dynamics" (most arguments still apply for juniors in the current market):
Printed a spreadsheet with how much I was earning annually, bonuses, performance, estimated salary adjustment in 6 months, 12 months etc.
Put this physical paper on the table and said: "I want to earn 30% more than this".
Two hours later, got an offer with such number.
Your number should be something you're happy (not simply comfortable) with. Like you'd go home all excited to take the job.
Don't be that guy who haggles on everything. In fact, if you encounter a person who haggles on a good offer, reject them. They would be the type who are either unappreciative of what you bring or always looking for more. Those types are dangerous in tech - they're likely to push more responsibility to you (e.g. testing, UI), get you to work after hours for free, manipulate you. They'll often find some excuse to turn down raises, bonuses, claims on benefits like sick days.
Sometimes neither side will name their price first. If forced into showing your hand first, don't highball. Just stick to your number.
If you get it easily, ask for more after sometime.