Focus on the early adopters in your niche who really need your solution. Do things that don't scale at first - reach out personally, offer white glove onboarding, be super responsive. Overdeliver on value to turn them into raving fans who spread the word. Collect their stories as powerful social proof to attract more customers.
Focus on building genuine relationships with your earliest customers. Reach out individually to understand their needs and give them special attention. Go the extra mile to provide value and turn them into champions for your product. Their testimonials and word-of-mouth referrals will be your most powerful marketing tool in the early days.