How to get better at blitz?

That is, I understand that playing (constantly) is part of improving, but what else to do? I mean, there must be something else besides playing that allows the improvement not to take too long. I hope you can share with me your experiences on how and how long it took you to improve either in blitz or rapid.

I would recommend not playing blitz as it doesn't improve your chess ability a lot, but playing longer games will help you improve at everything (including blitz if you decide to play it).

“Blitz chess kills your ideas.” - Bobby Fischer

To get better in Blitz, you got to practice to play fast without thinking long. But you have to make sure not to play wrong moves in hurry.

Few months ago, I was around your level and I would love to share things which worked for me to improve. First of all shift entirely to rapid games rather than blitzing daily. If you get better in rapid format trust me you will automatically crush in blitz. The reason is blitz is majorly intuition based and after playing in rapid your brain will take much lesser time to find the best or descent moves. It's hard to explain but our brain somehow eliminates the bad move and and leaves us with 2-3 good moves which takes lesser time to calculate. Once your chess "understanding" improves the faster formats will also show the results.
After achieving certain goal in rapid, start playing blitz. At first you will fall but once you get comfortable you will gain like 150-200 points. That's what happened with me. I majorly focused on rapid and classical format + tactics. Solve puzzles as much as you can. It improves calculation significantly and I personally experience that. Don't focus much on opening theory and gambits but rather focus on principles. I play shitty opening like Italian but still get to fair middlegame where tactics helps me. The only effort I took was to study basic endgames which most of the < 2000 here don't know. Like opposition and rook endgames.

1. Improve your tactics sensor and quick calculation.
2. Make practical decisions.
3. Practice.
4. Develop your intuitive play.
5. Openings study.

6. Analyze every game
7. Record every missed tactic & bad decision and study them periodically.

and, to expand on Invincible
...
2. ..... almost always it is much easier to attack, even material down, than to defend
5. ..... and pick openings which lead to a clear middlegame plan for your side and decisions that must be made for your opponent.

in my opinion 5 minute is a pretty decent time control... sometimes it feels short but its long enough to still calculate .. id go for an increment if you find yourself low on time... mix blitz up with rapid and with enough study and practice your sure to improve.. knowing when to sacrifice without calculating or not calculating enough and then realizing it doesnt work sucks.. but knowing certain themes that arise from the openings you play is gonna be key to not use that time calculating when you already know the pattern

"there must be something else besides playing that allows the improvement not to take too long"

Not a good sign (it's not a race).

Gosh, I need this advice too... even for 5 minute games.

I expect I'll be ranked about 2000 soon on correspondence, but 5 minute games I just blunder myself to losses against every 1200 on the site!

#2 agree

But, Blitz will help you to think fast!

But don't play hyper Bullet, ultrabullet
They are meaningless

Play classical like 30+0 , 40+0 etc.
It will help you to improve your chess!