Take the time to build up an expertise around a particular subject or skill. Most of you will already be well versed due to your profession. Spend time educating yourself so you know all there is to know about your area of choice.
When communicating with people, make sure that they know about your expertise. Consistently communicate your knowledge during meetings, emails, blogs, Twitter, etc. Make sure that people associate you with this subject matter expertise.
As your name gets associated with your expertise, people will start coming to you. Therefore, your network will grow. Opportunities will come your way such as guest speaking or writing, which will give you more exposure. At the same time, your existing network will better remember you.
Take the time to brand yourself around a particular expertise and you will be rewarded with a bigger and more diverse network. As a result, you will be seen as someone who others should get to know.