Startups, especially funded ones, are known for trying tons of flashy marketing ideas to try and draw attention to their idea or product. Whether it's sponsoring expensive parties or hiring celebrity endorsers or spending lavishly on PR, the idea seems to be to make a big splash and get in front of as many people as possible right away.
I'm not here to argue that these techniques have not worked for some people (Foursquare's SXSW unveiling was certainly a success), but a truly underrated startup marketing technique is the consistent email newsletter. I'm not just talking about email newsletter strategies for services firms, but also for social startups like Tumblr, Quora, Twitter, etc or product startups like Chubbies, Warby Parker, etc. It may not be the sexiest startup marketing tactic, but it works.
Many have called email the original social network, and that's because of its effectiveness of tying together large groups of people and how it lends itself to passing around content, and that's why it's so effective for marketing. Email remains the stickiest app of all: we're all on it, checking often, and are likely to click through on compelling content.
If you closely watch any successful social startup, they always seem to eventually start incorporating more and more email newsletters into their marketing. Twitter sends you the best tweets from your network in a given week, Tumblr sends weekly emails with the best posts from around the network, and it seems LinkedIn's online strategy is solely becoming emailing (spamming) posts from thought leaders.
As an example from my life, email is probably the only way I interact with several startups like Quora; I'm sent content every week, and if I'm intrigued, I'll click through and read it -- by using an email newsletter, Quora converts me from someone who would never use the network to someone who racks up 3-5 pageviews per week. In addition to the immediate boost of getting me there, it also keeps the network top of mind and makes me more likely to randomly check it in the future or advocate it to others. Without that newsletter, I would've forgot about Quora years ago rather than being a weekly reader, casual upvoter, and very occasional contributor.
Many startups think their startup may not be the best fit for a newsletter or they don't have the time to write one, but I'd challenge you to think through your options, and you can do it with an easy manual process of just inserting the best content into an email template. Some advice I recently gave to the founder of a website that lets you create and curate lists was to send out the most interesting lists each week to the network - for now, it didn't even need to be based on interest, just choose a nice variety. If you're a social-management tool like Buffer, blast out new features and also the most shared content. If you're a messaging app, let users know if other friends signed up this week and update them on new capabilities in the app.
You're working hard on your company each week and users are interacting with your site or product each week; leverage the work going in on both sides by incorporating it into an email. It can be once a week or once per month, but I'm sure that any frequency will drive people back to the app. The big social networks and product companies have demonstrated they value email newsletters, and it's smart for startups to start prioritizing them, too.