Before you start cataloging in Koha you'll want to set up your preferences and other rules.
Define your cataloging templates aka MARC Bibliographic Frameworks
Run the MARC Bibliographic Framework Test to be sure your changes are valid
Define any authorized values you might want to use in cataloging
Set up custom classification sources (if you use something other than the defaults)
Set up MARC matching rules for importing records from mrc files or Z39.50
Set up Koha to Keyword mapping for deciding how to display marc fields to the screen (still in beta - only one field)
Set up the Z39.50 targets you want to search for cataloging (and acquisitions)
Cataloging System Preferences
URLLinkText : Enter text to display when 856 fields do not have pre-defined labels
hide_marc : If you are unfamiliar with MARC you can have the MARC fields number hidden
LabelMARCView : Choose how you want duplicate fields to appear on the editor
DefaultClassificationSource : Choose which classification source is the default in your library
advancedMARCeditor : Decide if you need labels to appear on your MARC editor
marcflavour : Choose your MARC format
itemcallnumber : Enter which field and subfields to look into for the call number
MARCOrgCode : Enter your MARC Organizational Code (not the same as your OCLC number)
autoBarcode : Decide if Koha generates item barcodes for you
OpacSuppression : Decide if you want to hide items marked as suppressed from the OPAC search results
Set up your cron jobs
Decide when the system checks URLs in catalog records to see if they are still valid