Taken directly out of Mister_es sample code:
Code:
    ' Short explanation of the whole thing.
    '       1. Send a high level to all sensor input => GPIO<2:0>
    '       2. Read GPIO port 
    '       3. Send a low level to all sensor input
    '       4. Keep only GPIO<2:0> bits
    '       5. Test result
    '
    ' If no sensor has been touched, the result will be 7 => 0000 0111, case
    ' else, the body capacitance will introduce sufficient delay between
    ' step 1 and 2 wich will keep the according bit to 0.  
    '
    ' Results will be as follow
    '               NoSensor => 0000 0111 => 7
    '               GPIO.0   => 0000 0110 => 6
    '               GPIO.1   => 0000 0101 => 5
    '               GPIO.2   => 0000 0011 => 3
Seem like a pretty good description. If you are more specific, I am sure someone here can answer your question.