I've never tried it (though I keep meaning to...) but the wikipedia
entry for '4p4c'

http://en.wikipedia.org/wiki/4P4C

has a diagram which shows the 'usual' connections.

As Owain says, there is no guarantee about this. I have a Retell
Recorders box for recording via the headset lead; it has a six-way
switch to allow you to select the right wiring combination! From
talking to Retell some years ago I learned than 95% of telephones
correspond to their 'setting 1' or 'setting 2'. I haven't got my notes
on this to hand but suspect the wikipedia diagram is 'setting 1' and
might be worth a try.

HTH
J^n