We live in a technology age where everything is done via email, social media, and other technological means. Our email archives are chock full because we can easily search (well, if you use anything other than MacOS X Lion Mail, but that's a different story) to find what we're looking for.
So when I tell you what Alan Hess told me, which is to always print out your concert credential approval, a lot of you are going to laugh and say "well I can always get it on my phone if needed." However, I ran across a time last week where I did need it, and it was helpful to not have to search for it on my phone.
I had emailed back and forth with the Sister Hazel publicist a few weeks ago, and had filed away the email where she had given me approval to shoot, and printed it out while getting my gear ready for the concert. On Wednesday evening, I showed up to the venue. The venue manager was in the box office, and was completely confused when I said I was picking up a photo credential. There was no list, he didn't know I had prior approval, and definitely wasn't going to just randomly let me in with all my gear.
At that point I reached into my pocket, and whipped out the approval email from the publicist. He took it (see, another reason you want to print it out - so random manager doesn't take your phone) and went to contact the tour manager backstage. I'll note that it was about 30 degrees outside, and I was wearing a thin sweatshirt since I normally leave my jacket in the car so I don't have to deal with it (another reason to print it out - so you don't have to stand in the cold searching for that email).
A few minutes later he comes back and has made up a photo wristband and instructed the door guys and security at the front to let me shoot. Apparently the tour manager also thought I was a random person just showing up, and said "no," but once the venue manager showed him the email from the publicist, he had no problems with letting me in. I thanked the venue manager for his help, went in, shot the standard three songs per band (two openers and the main) from the side like I always do at this venue, and went about my merry way.
Always have a printout, it just makes things much easier.