Before setting off
Make sure you set the date and time on your camera correctly. Receiving a load of footage dated early January 2000 is a bit of a pain. Also make sure you practice filming as much as you can as this will help you get to know the limitations of your kit (and if anything isn't working).
Be ready to shoot
When something interesting could happen at any minute it's important to be ready to shoot all the time. This means your kit has to be ready all the time. You should have a nearly full battery and nearly empty media card in your camera, with spares of each on hand. You should keep all your kit organised, safe and secure for when you need it.
Set camera to auto
Best practice is to leave your camera set to 'auto'; focus, white-balance, exposure. If you find yourself changing any of these settings be sure to reset them back to auto afterwards.
Keep your lens clean and dry
Make sure your lens is clean and dry. Always use a lens-cap when you're not shooting and keep your camera in its case to protect it from dust, wet and impact. It is always a good idea to carry alcoholic lens wipes with you as well as lens cloths.
Pro tip: It may be also be a good idea to have a filter on the lens, this helps in brightly lit conditions as well as preventing the lens from getting damaged.
Check your capture is good
If you have time before you hit 'record' check your camera settings are all good, you've got enough battery and file-space and that you're capturing audio. If you can't check these before you record, check them as soon as you’ve started filming. Get into the habit of checking back over your footage regularly to ensure everything is working well. Especially if you keep switching between manual and auto settings.
Once you start recording, leave the camera rolling until the action is finished. Don't keep recording and stopping, even if you're changing camera angle. It's far quicker to keep the camera capturing, you're less likely to miss anything and you'll keep picking up valuable audio.
Pro tip: It is common for people not to hold their shots long enough when shooting aesthetic B-roll, once the shot is set up and you are recording, count to ten before stopping.
It's really important to keep your empty media cards away from your full ones (and your empty batteries away from the full ones). If you have any way of backing up footage as you go, back it up when you can. Try to keep things in a logical file structure so it's easy to tell when and where something was shot and you don't end up with duplicate filenames. The easiest way of doing this is by naming each folder by date.
It is good practice to make notes of what you have shot and what is covered in interviews. This makes it a lot easier when it comes to naming files and means that you know what you have covered and what order they come in. In your notes make sure you write down the Who, What, Where and When.
Make sure you keep your camera kit and computer stuff secure. It'd be a pain in the arse to lose your camera and worse to lose all your footage too. Don't leave any of it unattended, don't leave it in your vehicle overnight and be aware of leaving Gopros stuck on the outside of your vehicle.
Borders/ Police/ Restricted areas
Really expensive camera kit in really expensive flight cases attracts a lot of the wrong attention. Not just for sticky fingered officials but also for paranoid border guards who might decide you are a journalist or make you buy an expensive carnet.
Don't under any circumstances film borders, or military positions. If you are somewhere with tight controls on media be extra vigilant filming in any public place. Filming with a tripod, top-mic with deadcat, steadycam, big headphones, or a top light will always make you look like more a professional cameraman so avoid these if you're trying not to be noticed.
Pro tip: Crap looking bags attract less attention than posh kit bags. If you put your peli-case inside a cheap duffel bag and keep your media cards in an old pencil case you look less of a target to thieves and overzealous border officials.
Make sure your policy covers what you're doing, where you're doing it. Give your insurer an itemised list of all your kit before you travel, otherwise they might get twitchy if you come to claim. Lastly a 'new for old' policy is a wonderful thing, look out for them.