h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Here's another way that's easy to follow and will get you into a space that's about 4 feet longer than your car. I used to teach it to learners when I was a driving instructor.

Pull up parallel to the car in front of the space, about 3 feet past it and one foot away from it.

Reverse straight until your back bumper is in line with the other car's back bumper.

Still reversing slowly and steadily, apply full lock in the direction of the kerb. Be sure to take good observation here - the nose of your car is going to swing out quite wide.

When the bottom front corner of the window on your car (on the side nearest the kerb) is in line with the back bumper of the other car, apply full lock away from the kerb.

Just before you car lines up parallel with the kerb, straighten your front wheels.

You can do a 'gentler' version of the above (requiring a bigger space) by replacing 'full lock' with 'one turn towards the kerb', and then 'two turns away from the kerb'.

This may seem like an extreme parking manouvre but sometimes you just HAVE to get that space.
If it is possible, drive as fast as you can at 90 degrees to the space you want and in the centre. Then when you get to a distance that you think you can stop the vehicle safely simply apply the handbrake and turn to the left or right. Your car should then effortlessly slide into the space and you will be applauded by passers by for your supreme driving ability.
However, if you get it wrong you will cause a lot of damage so please be careful.
You will find this easier if you are in a a hire car because everybody does things a little differently in these.

The advantage of that method, should you get it right, is that you only need a space a few inches bigger than your car.

Of course you may not be able to get it out again, but if the owners of the cars either side of the space saw you parking they'd probably move their cars away fairly promptly.

To be honest with you, I would'nt blame them if they moved!