I went and practiced an opener for each matchup from imbabuilds.com on an empty map a few times to help get some of my muscle memory back and have a general plan for how i build things early game.
For ZvZ i generally 14 pool 16 hatch 16 gas with ling speed and baneling nest being my first gas expenditures. After that it heavily depends on how the game is going, generally i just go roach hydra with a focus on upgrades since i couldn't get mutas to work with the sporecrawler buff.
For ZvP I've been going for ling/hydra timing. I haven't quite figured out what the best thing to do for this is if i scout a gateway expand. So far I've been getting gas and a roach warren before my third.
For ZvT I'm doing the scarlett's 3 hatch build into ling/bling/muta.
I thought my rank would have been completely reset since it's been a very, very long time since i've played but i only had to play one placement game and was put in gold. That's where i was before, so I'm perfectly content with that.
So far the biggest things i need to improve on are scouting and macro, and doing both at the same time. I've definitely improved my macro in the 30 or so games i've played since starting again, but there's still room for improvement. Sometimes I overmake or miss overlords and set my production behind, or concentrate on my macro so much that i forget to scout and die to aggression that i definitely could have held if i saw it coming before they were at my doorstep.
I've also lost to a bunch of different terran stuff, like bio/hellbat pushes and blueflame hellions getting into my main because i fucked up my evo chamber/queen walloff but i'm not as worried about that yet. It's been a long time since I've played so I don't have a firm grasp on the meta yet, which will come with experience.
So far i think my favorite part about the game is that hydra speed is Lair tech now. Ling/hydra aggression is really fun in ZvP; makes the matchup much more fun than it was in WoL.