Defining Search Purpose

Identify keywords which will indicate the search's purpose. If I want to buy something online, suggest to users to use "buy+item name". If you are just looking for wallpapers, music videos, etc. which people made, you would use "entertain+item name". The search engine will therefore have more of the idea behind your search purpose and give you appropriate results. This is similar to what you already do by providing vertical searches after the user clicked search, but if you can provide some keywords which people might use with before their press search, it might improve search satisfaction.