Go To Tools->Preferences. On the left, choose 'Search'. On the right side it'll have a list of the search-engines already builtin which shows the keyword. To do a search, just type the keyword then the search term.
Google = "g search-term"
AllTheWeb = "a search-term"
No need for all of those search bars, you've already got one that fits all circumstances
That will show you how to add more searches to it. I have one set up to search my Everything Capcom Message Board (link in signature). "ec search-term"