Consider who you've been successful with so far. What do they have in common? Don't be afraid to go beyond the big buckets of B2C and B2B or healthcare, tech, etc. Think about level in the org, working style, business problems.

Then figure out how to get more. Once you know the answers to the first questions, then you can focus on where those kinds of people are.

I've discovered that we're really successful working with non-technical founders, or solo founders who need marketing support. This has led to thinking about my network and who might know others like this who could use our skills, beyond the usual suspects in our tech bubble in silicon valley.

I'd hyper segment. I've seen people build incredibly successful niches by finding segments like opthamologists offices and funeral homes. those groups have trade shows that are super hubs to expand; and once you succeed with a few, word of mouth helps you grow.