First, decide what you hope to gain from this position over what your current employer has to offer. If the only motivation is pay, then be prepared to pitch yourself as the absolute best and the most desirable candidate that will sit across from them. Otherwise, consider what else they have to offer over pay. There may be considerable growth opportunities or a benefits package with stock options that no one else can compete with. Determine what this job is worth to you outside of compensation.

Next, try to land on a realistic figure using your current earnings as a baseline. Contrast your earnings with your professional worth in your job market, and allow for a range of flexibility with that number. Examine the benefits you receive from your current employer. Write down any bonuses, stock options, or other incentives you receive. Consider your commute, retirement packages, PTO, etcetera. Next, examine where they're meeting, exceeding, or wanting in comparison. Be realistic and honest with yourself, and keep the negotiation open.