With my experience working in payroll and human resources I have seen that salary is a taboo subject and it should not be in regards to discussing this with your employer.
Everyone should be paid equally and NOT any less because of any protected characteristics.
1. Make sure you do your job market benchmarking in regards to the salary and job description for your current job or a new job.
If you are applying for an entry level role and you do not have the relevant experience in the field still do your research on a starting salary in your field and have the job market value in mind when negotiating.
2. Once you have done your research and compared your salary and responsibilities to job market value . Raise this informally with your manager and if there is no progress approach the human resources department.
3. Once you have your meeting ensure that you are aware of your emotional intelligence.
4. Keep calm and whatever the outcome do not take it personal.
5. When negotiating have your desired salary in mind but wait for the employer to start with the figures.
6. Be realistic and keep to your desired salary by giving a specific figure only when asked and do not give a salary range.
7. Use any leverage such as qualifications, tacit knowledge or another job offer to your advantage.