The most important survival tips some of us will ever learn: how to open a bottle of wine without a corkscrew.
Use a screw
Tighten a screw into the cork then use pliers or fingers to pull out the cork.
Instead of a screw you could use a hook or anything else that has a screw-like thread.
Hit the base
Remove any wrapping from over the top of the bottle (you might find a screw top at this stage).
Wrap the bottom of the bottle with a towel, t-shirt or anything similar that will prevent the glass chipping.
Hit the flat of the cushioned bottle bottom against a vertically inclined even surface such as a wall or tree. The force of the wine in the bottle hitting the cork will force the cork out.
Remove the cork with pliers or by hand when it is nearly completely out.
Instead of hitting the bottom of the bottle against a flat surface you could turn the bottle upside down and use the heal of a show or a block of wood to tap the base of the bottle with.
Push in the cork
Use a nail or a similar long and strong object to poke a hole into the cork to release pressure in the bottle.
Push in the cork using a marker, knife handle or other blunt object that is wider than the nail hole.
Be careful not to break the bottle.
Try not to get cork in the wine. If you do so you might need to use a strainer.
Use of these tips is at your own risk.