How to calculate new force field parameter?



hi,
 We need to calculate a MD of the protein with a small molecule.
 So, We calculated point charges of small molecule using gaussian
 and resp (in amber) .
 To run MD, We also need bond, angle, torsion, improper torsion
 and VDW parameters of a small molecule.
 Does anyone know any information (e.g. web or paper)
 for beginners that indicate how to calculate it?
 K, Watanabe.
 Hitachi ulsi systems co. ltd.