This part is just a numbers game. Work with more people and those people can recommend you. Within your company work with other people in your group and other groups. Don’t just stick with your friends.
Work with people in other departments. Those guys in marketing are actually good at marketing. They will also expand your network faster than most engineers.
Work with other companies. A chance to talk to customers is a bonus. Take every opportunity to find out how they are using your products. Take a special interest in them and they will remember you.
Work with other projects. Open source can be a big help here and we’ll talk more about that in building your personal brand.