Pearl,
Though it's very naïve to ask, what are the most common errors, you'd face when writing a Cobol program, here's a post, that might be of interest to you -
External link removed. And moderators, pardon me for referring an external URL.
Also, to generate a complete listing of all possible errors in Cobol, along with the error-codes and their descriptions, write a Cobol program, with the PROGRAM-ID ERRMSG, compile it and look at the listing in the Spool.
IDENTIFICATION DIVISION.
PROGRAM-ID. ERRMSG.
Thank you very much.