Future earnings generally are a percentage of your current salary, so your lifetime earnings could be significantly higher when you negotiate. Also, most employers expect applicants to negotiate.
Research what the market pay is for your industry area. There may be differences based on experience level, cost of living in the city, company/organization size and type.
Negotiate salary after you receive a job offer. This allows you to know what the employer is willing to pay so you don’t price yourself too low.