When going outside I normally don’t think about health & safety as it’s just a usual part of everyday life. However while working outdoors a lot of threats should be considered.
Outdoors environment can’t be controlled by us in the terms of one-day-photoshoot.That means that you should consider road and ground condition (is it slippery or muddy, or do rocks fall off crags) as well as the weather (hot summer sun can be the cause of skin burns and heat stroke, cold and wet winter air may cause frostbite and prolonged illness while the strong wind may bring down trees or unwanted objects on your head). So think twice about footwear, clothing, protective creams and gear before hunting for images. For some advises please visit HSE website.
Think about the area you’re going to work at, consider having a permission for photoshooting. In some places it’s illegal to take photographs, in some you need to get/buy a permission while in others you can work freely.
If you’re photographing in a public place think about risks you may cause to others. Photographic equipment or other belongings left on the ground could be a reason of someone’s fall and injuries. You can bowl down someone accidentally by moving back or aside while looking in camera. So think where to store everything and be cautious.
Consider having different types of insurance: for your equipment, vehicle and public liability insurance.
If working with models outdoors you should make them aware of these health and safety risks and make sure they follow precautions.
To find out risks of a location you can read about the place, talk to someone who has already been there and visit it yourself before the actual photoshooting.