How to make iPhone battery last all day?

So i'm going to a concert tomorrow. We're leaving at 10am to arrive at the hotel for 2pm ish. I'm not going to use my phone in the car at all, but I don't know whether to switch the phone off completely or leave it on but just not use it. What will save the most battery because people have said it drains it if it's switched off?

When I get to the hotel I can't charge the phone because I leave to go straight to the concert and i'm going to want to take photos/videos at the concert so I want a lot of battery for that. The concert lasts around 5 hours because there's the supporting acts aswell who I want to take photos/videos of but I want it to be able to last until the main band aswell.

So basically has anyone got any advice on how I can make my phone last a 3 hour journey and then a 3-5 hour concert including taking photos/videos aswell.

Just charge it to 100% then turn it off and don't turn it back on until the concert starts

Leave it on, you don't have to turn it off as mine doesn't lose power when it goes dormant, but put it in airplane mode and make sure Wi-Fi and bluetooth are off. That means it won't attempt to get signals, so basically its just a camera for your use. Although concerts are usually too dark or too bright (flashing lights) for cellphone cameras. Even with iphone 5S having the low light photo taking features built in, they still aren't like a regular camera when it comes to dark / light, they always have problems with that.