Figure out where you want to sit before buying your tickets. If you are tall and enjoy moshing, general admission might be the place for you. If you are on the shorter side try getting seats up high to avoid having heads in your view!
Eat beforehand. There is nothing worse than standing in line right when the band starts playing. And buying merch is a double edged sword, either you can avoid queues and miss the opening act or deal with lines and out-of-stock signs after the concert.
Remember personal space. If the venue is indoors then the room will be hot and stuffy already, so try not to crowd anyone.
Be courteous. Understand that concerts can be hectic so if the guy in front of you is taking eons to walk up a flight of stairs, take a deep breath and relax; you will get there eventually.
Take a picture of your parking section so you can avoid the traffic when you try to leave the concert hall.
Be cautious of your surroundings. If someone is standing too close to you or making you uncomfortable feel free to move away. If you are in a seat and cannot move, some concert calls have a number you can call to report people or have security find you a different seat.
If you don’t know what to wear, remember that at most concerts you will be standing and dancing most of the night so you might want to opt for more comfortable shoes. Also the temperature at concerts seem to have a mind of its own, so wear layers to avoid getting too hot or too cold.
Enjoy the concert! After all the stress of getting there, dance like nobody’s watching!