Hi Ela,
most guides for SAP CRM Web UI Business Transaction Search Enhancement tell you how to implement a BADI or how to hack the search query object even in cases you just want to add some simple fields as search criteria or result list field.
Because I don´t wanted to develop in cases it is not needed, I searched for a better solution. And I found it. I hope my solution will help you too.
http://www.hybrid-eichhoernchen.de/business-transaction-search-enhancement/
Kind regards,
Peter