Chem Lab Drug Molecule Design?

I'm given a hypothetical receptor site with clear in your mind molecular fragments sticking out of the receptor site. I know the bond lengths of these fragments and the total size of the site. I stipulation to know how I'm supposed to figure out which drug mole will best interact and in truth FIT into this site!! It's supposed to be an organic compound beside a strong electrostativ attraction between the drug and receptor. Do the following:
A) are there any charged fragments ( for example Argenine or Lysine)? If so later your drug should contain the OPPOSITE charge, for electrostatic interaction. If not your drug should not contain charged units.
B) Are in attendance any benzene (or other aromatic) fragments? If so then your drug should also contain molecules beside a pi (double) bond for pi-pi stacking (interactions).
C) Are their any fragments that can produce hydrogen bonds (hydrogens that are connected to O,N,F atoms)? If so then your drug should also know how to form that kind of bond (i.e. also contain H bonded to O,N,F).
D) Does your site contain long cuff aliphatic molecules? If it does then their is a strong steric hindrance and your drug should be a very small molecule.
Hope it help