Locating a shelter
Staying warm and dry is a priority. Beware of loose rocks under cliffs. Falling coconuts can kill too. Being close to clean water is a bonus, and dry wood for a fire.
Building a shelter
A wall of rocks is better than nothing. If you can find branches erect a simple lean-to, thatched with smaller branches and grass. Lay a floor of leaves and straw.
Building a fire
Start with small dry material like straw and tiny twigs, prop larger twigs above it, and larger ones above them. Add logs when it’s going well.
Igniting a fire
Shorting a battery can create a spark that will ignite your tinder with a little gentle blowing. Otherwise look for rocks that spark when struck. A useful piece of outdoor survival equipment to carry with you on a key-ring is a fire-lighting steel – get one from any bushcraft shop (try http://www.angloforro.co.uk/product-category/survival/equipment/).
Boil water if you have a container to boil it in, since all water from an unknown source could contain impurities. Rain, snow and morning dew are all safer. You can also squeeze water from fleshy plants, like thistles and cacti.
Water by transpiration
Slip a plastic bag over a leafy plant and tie it at the neck. After a few hours, especially in warm weather, drinkable moisture collects on the inside.
Identifying plants you can eat isn’t easy, but most ordinary leaves will not be highly poisonous – try a small amount and wait. Observing what wildlife is eating is a guide, but not a reliable one.
A multi-pronged spear is the easiest way to catch small wildlife, both in water and on land.
Even in cloud, you can usually tell which direction is brightest (especially at dawn and dusk). This will give you your compass bearings.
Find the constellation of the plough, the last two stars point toward Polaris. This is due north. If there’s a crescent moon, a line through the horns of the crescent down to the horizon is south.
You never know when you’ll need one, so memorise a few. There’s a good reference here: http://www.realknots.com/knots/.
Fire is good, but a mirror made of anything shiny is also very effective in sunlight.