…is a frequent question music students and pre-professionals ask. Here’s a strategy you might consider:
First, ask yourself, what is my minimum? If the offered price is less than your minimum, it’s not worth your while and you don’t do the gig. Never undercut yourself.
Second, what do I think is the maximum asking price where the buyer will still be willing to hire? If a buyer says no to $1001, but yes to $1000, $1000 is your maximum. Figuring this out takes practice and experience.
You have your minimum and your (speculative) maximum. Time to negotiate! You want to get closer to their maximum and they want to get closer to your minimum. Good luck!