Maybe you're new, maybe you've been here before.. A lot has changed if you're an old returning player, and there's a lot to learn if you're new.
This is just a collection of things that I have found to be helpful!
The only place you can play the current version of DDR in the US is Round1.
Konami and Round1 have an exclusive arrangement for the current version of DDR. Dave & Busters used to be somewhat current, but their machines are now stuck on DDR A20+. There may be other independent arcades running semi-recent versions of the game on unofficial servers.
Get an e-amusement pass
e-amusement passes basically allow you to have a user account that saves scores. They're sold at the counter at Round1, and if you're at an independent arcade that has their rhythm games running on unofficial servers, they probably sell them there as well. I bought my e-amusement pass quite a while ago, but I believe it was $6 or $7. You can register the pass on Konami's website for some additional features.
Talk to your fellow footgamers
The good players seem very intimidating. They're not! It's rare that anyone is just a cocky and naturally talented player. Pretty much everyone put in a lot of sweat and time to get to where they are, and if you're wanting to get better at the game and are committed then I promise that people will not look down on you. Find someone around your skill level, add them to your rival list and try to beat their scores. You'll probably play stuff you wouldn't typically and expand your skillset. Playing with others and talking about charts is a great way to improve yourself and make some great friends!
Use a score tracker
This is for when you're a bit more advanced, but third party score trackers are wonderful. I use 3icecream. You'll need to have a Japanese region Konami account and pay for a basic course subscription (it's $3 or $4 a month, I think), but it's so worth it. This is a very physical game. Sometimes, you just have a bad session. Sometimes you have a streak of bad sessions. It's easy to get down on yourself and beat yourself up. I've found that using a score tracker helps me stay positive. Even if I had a bad session, I'll refresh my scores and I usually find that it wasn't as bad as I thought. I did fine! Of course, sometimes you do have a truly bad session, but sometimes you're just totally wrong!
Yes, this is an extremely physical game and you do need a bit of fitness
I remember seeing a comment online fairly recently from a pretty new player who was whining about the difficulty a bit and said something like "really? you just have to be an athlete to play this?" Maybe not quite an athlete, but yes... you're going to sweat a lot and if you're not in good shape, you'll start to get there. There are going to be walls where your fitness isn't good enough, and you're just going to have to beat the absolute hell out of yourself for a while until it starts getting easier. Drink a lot of water when you play! Drink some sports drinks (I like Gatorlyte a lot). And... pay attention to your diet. I'm in my 30s, but I think even if I was younger I probably wouldn't have a great session if I ate a whole pizza and 10 beers the night before I played.
Learn proper technique early on
Did a pattern feel kind of funny and you had to use one foot to step multiple times? That pattern was probably a crossover and you just double stepped it. You can get away with it sometimes. Sometimes it blows up in your face. It's better to just learn to actually do crossovers. I was a terminal double stepper until fairly recently, and I wish I had just gotten over that hump way earlier on.
DO NOT BE A DDR BOOMER
You played back when Extreme was popular? Cool. The world moved on long, long ago. That was over two decades ago. I know it doesn't seem that long ago, but it was. DDR did not stop existing while you stopped playing.
Look, I get it. It was rough for me coming back, too. Most of the Extreme songs are still there. You can still play them. But the game has vastly improved since then. Charting is better, the speed mods are better, literally everything is better.
There are over 1,000 songs in the game now. Play them. Experience something new. I have had way too many DDR boomers approach me and say "wow, I really hate the anime music" or "wow, I hate this UI, I see why reddit said it was bad." I am not impressed and no one else will be. We play this game because we like it. That's fine if you don't, but don't expect to impress anyone who is committed to it. Adapt and enjoy, or go find a beat up old cab to play on somewhere else.
Bar tribalism is dead and buried
The bar vs. no bar debate ended long ago. It is fine to use the bar now, and the vast majority of players do so. There is no shame in the bar. Simply passing is not the objective anymore, people overwhelmingly play for score now. The baseline difficulty has also increased a lot.
If you want to play no bar, you can. I genuinely think nobarben is one of the most impressive players out there by managing to keep up with playing no bar under the modern difficulty. I played no bar when I started again, but I found that I just couldn't keep up past 13s. I'm not light enough on my feet without shifting my weight. Like the DDR boomer, no one will be impressed if you drop "bar raper" like it's 2006.