Get a long length of clear tube, put one end in the fuel tank, suck on the other end until the fuel is nearly at the end, then put your thumb over the opening and place the other end in a fuel can, remove thumb and petrol should flow into fuel can.
Obviously be very careful when doing this as the fumes could give you a nasty headache so make sure there is plenty of ventilation and a mouthful of petrol is not recommended.
To add to what Mattie says, when you take your thumb off the tube, the end of the tube should be lower than the car's fuel tank, or the petrol will just run back into the tank.
You can buy a syphoning pump (plastic thing) or, if you have a long pice of tube feed it into the tank and then put your thumb over the end and pull the tubing out until you can see petrol in it, then keep pulling until the petrol is lower than the tank and the petrol should syphon out. I have used the latter before - a bit tricky but better than a mouth full of petrol!!
after about 1992, fords were fitted with anti syphon devices, so you wont even get the tube in. if youre scrapping the car, bang 2 nails thru, and remove them at the same time, one to aerate, the other will pour. dont use a drill, you can guess what happens if it sparks.....!