How do I prepare a PDB for submission to the Protein Data Bank?
These two links go through the specifications required for the PDB format:

Link1: http://deposit.rcsb.org/adit/docs/pdb_atom_format.html

Link1 primarily goes through the specs. required if you say have a NMR file you would therefore require the MODEL statement. It also goes through other statements such as when to use TER and how each ATOM line should look etc...

Link2: http://www.wwpdb.org/documentation/format33/v3.3.html

Link2 goes through the other statements such as HEADER, REMARKS and TITLE