Ask IH: Which one was your best channel to acquire organic users, and how?

I did all of the following at various times on LinkedIn or with LinkedIn connections to develop my newsletter subscriber list. It's a curated newsletter about Influencer Marketing (for those in the industry)

Here you go:

• Directly connect with people I think will most likely benefit. (~500-700 a week connection requests got 50 subscribers a week. (rough math)
• Direct Message existing connections (I will do this when I have an interesting piece of content that I'd like to get to specific people)
• Email existing connections (I did this initially and got 100 subscribers in one week)
• Post on Linkedin Groups (this doesn't work super well, or at all from what I can tell. Depends on your use of groups and if they are active)
• Post on LinkedIn ( a variety of ways to do this
• Get others to post on LinkedIn (I've directly emailed people I think would benefit personally from speaking about me, you can call this influencer marketing)