One of the most noticeable things about going on an adventure is the unfamiliar environment you'll encounter. This works tenfold for your kit.
Shooting in harsh environments
Before setting off invest in camera covers and dry bags. Also buy lots of little bags of silica gel to put inside your camera bag. If you can't get silica gel, you could try buying a load of disposable nappies and cutting out the absorbent strip (one of those can hold a litre of water).
Salt water is very corrosive to your kit so make sure you are very aware of this, if things such as memory card holders or bags have gotten wet from sea water, rinse them off with fresh water to make sure the salt water doesn’t do too much damage. Even if your camera looks clean and dry, it can still be damp/ salty, clean electrical contacts with alcohol wipes
Let your camera dry completely before removing batteries or cards - water getting into these areas can really damage the camera so make sure the external of the camera is dry. This also applies to GoPros- be careful to make sure the protective case is dry and clear of salt water before opening it up.
A polarising filter on your lens will help cut down glare and improve colour saturation.
A common issue when filming in very cold conditions is battery life. Batteries drain much quicker in temperatures below freezing. Make sure you always have a lot of charged batteries and try and keep them warm if you can.
Also try to keep your camera as warm as you can while outside, your kit is not built for temperatures below zero so try to keep it warm. Keep it in your bag until it is time to start filming and then put it away straight after.
Make sure your kit doesn’t change temperature too quickly, for example, don’t take your camera from outside to inside a warm house as this can cause condensation to form, put your kit into a plastic bag and leave it in a cold place in the house so it can gradually warm up.
If snow gets on the lens, do not blow it off, wipe it off with a brush or cloth as blowing on it can cause moisture to get on the lens and freeze. Also, do not change lenses outside as this can cause moisture to get inside the camera and freeze.
Bring protective kit and cut down on camera kit. Make sure you bring weatherproof containers for your SD cards and covers for your equipment. Cut down the amount of actual camera kit you bring, carrying too much will tire you out and there is a higher chance of breakages.
If filming in the snow, it is common for the image to look very over exposed so you have to make sure your subject is exposed correctly, although the background may be over exposed. Breaking up the background by placing your subject in front of some trees or something like that can help to stop the background looking so over-exposed. It is good to use a polarising filter on your camera if filming in the snow as it reduces the glare that snow often causes. Also make sure you check your white balance in the snow as if you get this wrong it will look very wrong.
Use a filter to protect the lens from dust and dirt, it is also easier to clean a filter than an actual lens. Make sure you clean your kit very regularly, use wipes and brushes to get dust or sand off your kit. Just do not let dust or sand settle.
If you're not using your camera or kit make sure they're stowed aways and their bags/ cases are securely shut.
Like in any harsh environment, avoid changing lenses regularly and only do this when you are sheltered and your kit is clean. The same rule goes for changing batteries and SD cards- avoid dust entering the camera and keep the batteries and SD cards safe.
Protect your camera from the heat as much as possible, if you wish, you can buy heat protective bags and covers but also make sure you keep it in a shady place. Cameras can easily overheat avoid having them in direct sun as much as possible. This is especially important in places like car dashboards which can get heated by the engine too.
It is useful to have shade for the camera when you film as well, this is in order to help you see the screen and avoid too much glare. Lens hoods are useful for the latter reason.