As long as you give the right answers to the Immigration Officer..no. You just go up to the desk, they confirm a few details, and assuming you are not carrying an Armalite, they let you in!
What do you mean confirm a few deatils? do they run a check on your passport? I received a caution a few years ago for something and am scared they won't let me in without a visa.
They just ask your name, address, occupation. Are you on business or tourist; that sort of thing. As long as your passport looks OK, they just let you in. Oh, you must have a passport with the digital lines on the back page (ie the new burgundy coloured one, not the old dark blue one).
Yes, they do check your passport against their database. Yes, the questions about your visit can be detailed. If your caution was in the US they may well have your details on record, if it was to do with drugs then you cannot give the correct answer to the visa waiver form.