For startups, the most effective customer acquisition channels depend on factors like product Margins, audience targeting options, and demographic fit. Paid channels like Facebook and Google Ads work best for high margin products or those with high referral rates. Unpaid channels like Content Marketing, SEO and word-of-mouth require more effort but are less volatile. The author recommends prioritizing "persistence channels" that provide compounding returns over "hit-or-miss" channels that rely on going viral. Overall, startups should test multiple channels while focusing on those that best match their product and audience.