There's a difference between marketing to existing clients and new prospects. With the former, you don't have to build credibility and you can personalize your approaches. With the latter, you're best off with referrals and public IP, such as books
If you want to be able to talk to almost anyone about almost anything, read widely. The worst books to read are business books. Read fiction, biography, history, science, philosophy, and so on. Read books on the best-seller lists. This is
A great many professionals try to mix their clients with their prospects to create "evangelism" which will forge new business. Fair enough. But think about this: Your fastest and best route to new business is to specifically mix your best clients
If you think you're in the marketing business, but you're afraid to make predictions, or to criticize some popular position, or point out approaches that are bogus, or take strong stands, then you ONLY THINK you're in the marketing business.
The more "attractors" you lure into your community, the more they will, in turn, attract still others. Don't simply look for quantity for your lists and activities, instead seek quality. "Quality" here consists of people whom others will readily be