Ask HN: How do I market to millennials online?

I'm a Gen-Xer trying to sell products whose target audience is people in their 20s and early 30s, who are getting married or having their first child, or who have a lot of friends who are doing so. I'm increasingly feeling like I'm an old fogey who doesn't know where people younger than me are congregating online, or how to market to them. I'm more of the FB generation than the Instagram/Snapchat generation, and honestly I don't even know if it's accurate that Instagram/Snapchat are where I should focus. I would love to hear from people who are in the 20s and early 30s, or who feel like they know how to connect with them. What's a good way to get the word out about a new product? Will traditional online ads fall on deaf ears? What sort of out-of-the-box strategies are likely to connect with this demographic?