So I've been to a lot of concerts including Bastille, Panic! At The Disco, Twenty One Pilots, Fall Out Boy, Ed Sheeran, etc. I think this makes me qualified to give some rookies some advice on how to survive a concert or music festival.
Concerts: What to bring and how to survive
Fully charged phone with plenty of storage space - this is essential. If you're anything like me, you want to document the amazing time you had and that means taking lots of pictures and videos. Make sure your phone is fully charged because taking videos drains the power fast, and make sure that you have plenty of storage so you don't have delete apps in the middle of the concert to make space for your photos.
Ear Plugs - I know what you're thinking, ear plugs are for the weak, I thought that too. But then my first concert I was stuck right in front of the speakers and I couldn't hear properly for 2 days. Concerts are loud and your ears might need a rest so do yourself a favor and and buy some $2 ear plugs.
Money, and lots of it - You are going to want to buy some merch, I can guarantee it. Concert t-shirts usually cost between $30 - $50, so save up. Sweatshirts, posters, hats, etc are also available for sale, so I would bring about $80 just to be safe.
Now that we have the essentials, you're going to want to keep your phone and money in your front pocket. This makes it so it’s hard to be pick pocketed, and that happens a lot at concerts, so keep your mula safe.
I recommend getting to the concert an hour - 3 hours early. This is so you can get some good merch and if you're in the mosh pit or have general admission you can get a good spot right in front of the stage. Speaking of merch, get it before the concerts starts. You want to do this because it sells out fast and after the concert you probably don't want to stick around in a long line to buy a t-shirt.
Have fun! Once the concert starts, don't give a crap about what people might think of you. Sing as loud as you want and break out some dance moves, just don't be that person everyone wants to kill, there is always someone who just doesn't make the concert fun for everyone.
Music Festivals: How to survive
To be honest, I've only been to one music festival, but I learned a lot. It's like a concert times 7. You're going to want to bring what you would a concert, plus a little extra. Before you go, check the weather, most festivals are outside. Don't be afraid to bring a rain jacket and warm coat, at my festival it was raining/snowing, so dress appropriately, I know you might think it’s uncool to wear a coat to a festival, but it’s uncool to freezing cold too.
You're going to have to deal with a bunch of weirdos at festivals, no avoiding it. There is almost always beer being sold somewhere so you might run into a few drunk people, just ignore them and get as far away as possible from them. And to be honest, you might get a beer thrown at you, I did and my hair smelled like cheap beer the rest of the night, so just be prepared.
There will be merch being sold, so I would go buy some while a band you don't know/like is playing. There will usually be less people in the line and it's nice to get out of your seat/the pit for a while. In fact, there are usually booths around so feel free to explore them, it's pretty fun.
I hope this was helpful! Just make sure to have fun at your concert or festival and it will turn out to be awesome.