Identify and target groups and connections which are relevant to your aims and capabilities.
Relevance can be according to several different things, for example: geography, size, sector, social grouping, political or religious grouping, trade or society grouping, academic or technical grouping, and other common interests.
The more relevant your targeting of groups and contacts, the more useful your meetings and referrals will be.
Other professional people can be important networking contacts. Don't limit your targeting just to obvious business people.
Certain non-business professional people can be hugely influential in networks, and greatly trusted because of their neutrality and professional standing - educators and scientists, for example. Journalists, surgeons, and magistrates, also. There are many others. It is not easy to make connections with these people through conventional business networking, but remember that a network is not only made of business-people, and be awake to these non-commercial connections when the chance comes.
If you find that your networking is producing very low opportunities for follow up and referral, try to improve your targeting. Find different groups and methods, in other words.
A true business network is a connected system of people within which referrals and opportunities can be passed through several connections, or circulated to all those connected. Networking thus can extend far beyond simply having lots of random one-to-one meetings.
A given number of people who are connected for a reason will generally be more productive than the same number of random connections.
So don't go aimlessly after every networking opportunity which comes your way; instead try to find networks which already function well or have the potential to do so; and consider and decide which sort of groups and contacts will be most helpful for your aims and capabilities - ideally remembering that you need to be able to help them, as well as they should be able to help you.
Within most networks people tend to have a few close and trusted connections. Choose these, your most trusted and closest associates, very carefully.
Reputations are built according to your chosen contacts, in addition to how you yourself behave.
The old expression is generally true: "You can tell a man by the company he keeps..." (or woman of course).
So focus your efforts on groups and connections of integrity, as well as relevance.