I agree with herveus. Indexes always doesnot suit all tables in the database (DB).
Since you said you have the log file at hand .
Find out the tables that have large amount of data , in here if the data is only inserted or queried , you can go ahead and index them .If update/Delete happen too often indexing would not be such a great thing as the indexes are built each time you update the DB.
indexing is a tricky thing , you have to observe how ur DB behaves in production environment . indexing should be carried out only (querying)fetching is more.
Regards, Swaroop