As you are probably already aware, Sitefinity utilizes the Lucene Search engine. Basically you need to index somehow content in text format (creating your index catalog). Then search for it.
In Sitefinity you can specify how different terms in your query should be parsed e.g.(home+services+industry
) can be set to search for (home AND services AND industry) or (home OR services OR industry). This depends on the mode of the search e.g. AllWords or "AnyWord".
One way of implementing Search By Category would be to create separate indexes for the different categories of content. This would cause different result sets based on category.
All the best,
the Telerik team
Check out Telerik Trainer
, the state of the art learning tool for Telerik products.