Firstly, is the people you work with on a daily basis. Get to know them better. Find out how you can help them. Being of service to another without expectations of something in return can be one of the best ways to grow your network. This includes getting to know your supervisors and managers.

Secondly, expand your circle of contacts. Who are your customers, clients and people you deal with on a regular basis that aren’t fellow employees?

Thirdly, is to think of a bigger picture. What industry do you work in? Do they have professional development or training opportunities? This can put you in contact with people in the same industry, yet working for a different company.

Does your industry have an Association? Associations often have annual or more often meetings where you can attend and get a larger and more diverse group of potential contacts.

As originally answered on Quora.com.