First get your data organized in MS-Excel. Things we had to watch out for were: date formats to match your Koha / mysql date formats, barcode, itemtype, library branch. We had to add last three to the Excel data. Also watch out for common things like quote, comma, tab marks & any unusual characters in your data. Clean up the data thoroughly.
Then save the Excel file as Unicode text. Excel saves as a tab delimited file in Unicode. We need UTF-8. So you need some text editor which can save the file as UTF-8, like EditPlus or Kate (on Linux)
After you have saved the file as UTF-8 text, start the Delimited Text translation Wizard from the MarcEdit program group. On the second screen give imput and output (i/p and o/p) filenames, leave the delimiter to tab, put text qualifier if any in your text file, click on Edit LDR/008 select LDR dropdown appropriate to your data. Select UTF-8 encoded checkbox.
On next screen you have to build a mapping from your Excel file columns to Koha marc tags. Trick is to click in the Select Field 0 drop box and while it is selected type your corresponding marc tag in the map to text box. then click apply. Once you have mapped all columns in your Excel file to Koha marc tags, click on save template so you can reuse it next time you import data in the same Excel format and click finish. It will save your template as a .mrd file and create a .mrk file of your text data.
Open the .mrk file in MarcEdit by double clicking it and simply click on the Compile Records button. This will compile all your records and give you a .mrc file.
In Koha go to tools – > Stage marc records for import, select your .mrc file set record matching rules needed and click the big button. This will import the data in staging area and take you to a summary page which will have a link to manage the imported records. Click the link select record matching conditions needed and import the staged records in to the database..
Reindex your database by running misc/migration_tools/rebuild_zebra.pl -b -w ( or by running misc/migration_tools/rebuild_nozebra.pl if not using zebra. )