Have you had a look at the CRUD code generated by Yii 1.1.1? It now generates some search code in the model and the admin view. This might be worth a look.
If I have complex searches for a particular model I tend to create a new class (eg QuestionSearch), in this class I have all the search criteria as properties, and I generate the criteria required for the search. I also use the same class to make a textual description of the search (eg. searched for all questions by John with the Swimming tag).