The best advice I was given when looking to get into human rights was to volunteer as soon as possible in something that interests you. The skills you learn will be transferable to human rights or development.
Networking is what you make of it. If you are the sort of person who is happy to meet new people, chat with them and keep in contact with them, then acting in that way would be second nature, and for me that is largely what networking is about.
Do your research on… the specific organisation, on the department you are applying to, and if you are contacting an officer directly, take interest in the work that they are involved in. This will help you to write a strong application.