I would help user retention via upvoting those who been around for months (and are making an effort) but still see their post barely crossing the dust threshold. I would do this via giving them a delegation that can help them sustain their blog and upvote support. Depending on the amount of Steem I have, I would also create a small team to help out with this task and other user retention related tasks such as commenting on new user posts.
Perhaps star an umbrella program.
Create 4 dolphins in which help out two Minnows each who in return then help out 2 redfish each. As each one grows to the next step they are asked to follow the above guidelines so the help umbrella reaches as many as possible and would eventually be self sustaining.