This comprehensive list was first presented in the book, Traction - How Any Startup Can Achieve Explosive Customer Growth, by Gabriel Weinberg and Justin Mares.
Note: Not all channels suit every phase of growth. Depending on your business model, one may work well for acquiring your first 500 customers, but not scale well for finding your next 5,000.
Advertising, writing or sponsoring articles on blogs that serve your target market. It can also include creating unique special offers for a blog's audience.
Getting coverage on TV, radio, newspapers and other traditional outlets.
Typically from publicity stunts that get media coverage, or providing newsworthy service to your customers (e.g. the dentist providing a Japanese tea ceremony to patients, or a book vendor making deliveries by drone).
Paid advertising in search engines such as Google with Google Adwords and Bing with Bing Ads.
Facebook ads, Google Content Network and Remarketing, Adroll etc.
Anything from billboards, to magazine and newspaper ads, or flyer distribution.
Getting your website to show up at the top of key search results.
Usually this entails providing valuable information to your target audience via blogs, newsletters or special downloads such as ebooks, white papers or case studies.
One of the most powerful and important marketing channels available to any business. Most serious marketers engage in some form of email marketing.
Free apps, websites and other digital tools that provide a valuable service to a target audience, converting their users to leads, e.g. a calorie counting app for a weight loss company.
Enticing customers and members of the public to refer new customers. Dropbox is an example of a business that created an exponential growth trajectory for itself by offering customers additional storage space for referring friends and colleagues.
Strategic alliances, host beneficiary and other arrangements with non-competing businesses that serve the same market. A simple example of a strategic alliance might be a restaurant offering a meal deal that includes tickets for the neighbouring cinema, or credit card companies who offer air miles with purchases.
The timeless business of exchanging products and services directly for cash, aided by systematic methods for improving the sales process, e.g. "Do you want fries with that?"
Getting others to sell your products for a commission.
Selling your products through platforms with tens or hundreds of millions of users such as Ebay, Ali Baba, Amazon, iTunes, Google Play, Youtube and Facebook.
Industry focused trade shows can be a very effective way to connect with large customers, as well as laying the groundwork for profitable alliances.
From small local meetups to specialist conferences, some businesses have used offline events to drive spectacular growth. Two household names include Tupperware and Weight Watchers. Offline events are equally effective for B2B situations, too.
Whether for local business groups, professional conferences, major trade shows or other events, there's a perpetual need for public speakers who can tell interesting stories about problems they solve. Speakers enjoy the special privilege of holding the floor for the duration of their talk. With the right presentation an uncontested slice of audience attention is extremely valuable and very hard to find through other channels.
Whether online or offline, successful community driven business models have some enviable qualities that are hard to create by other means. They can grow exponentially with minimal marketing spend, be self sustaining, long-lived and enjoy unusually high levels of trust, respect and even affection from community members.
Examples include businesses that create or sponsor professional or hobbyist associations, online forums or businesses connected with open source software communities. Examples include Automattic, the company behind Wordpress.com (now valued at over US$ 1 billion) , the online forums Whirlpool.com.au and Stackexchange.com.
I strongly recommend the book that inspired this post. You can download the first three chapters of it free here: Traction.