I spend my time engaging the community at large. Upvoting other posts definitely helps, and you should do that! You should also comment on other people's posts, even if it's a "that's awesome, nice job!"
Something as simple as that can build rapport with the person, and they just might be inclined to return the favor. Also, get involved with dApps. A lot of them will give you Hive for delegating to them. (don't do this unless you have at least 100HP to delgeate. Most dApps will thank you, but if you're in it to invest, they're not going to give you any ROI) Others will upvote your content for using their app. @vimm does this for their streamers. It's not uncommon to see myself or my co-owner also go around and throw out upvotes like they're candy.
What about you? What's your strat?
I upvote and leave comments. On top of that, I also buy some through exchanges every week or so.
Smart. I've been placing regular buy orders last year and into this year to bolster my HP, too. Now it's finally reaching the point where my upvotes actually mean something!