I frequently hear the attack on Pearl Harbor was meant to destroy the US Pacific fleet and "shock" the US into seeking peace terms. What exactly were the Japanese hoping to impose on the Americans in the event they sought a negotiated peace?
Precisely as Albino says, it was more a delaying tactic than an attempt to keep the US out of the war. It's kind of apparent in that wonderful quote attributed to Isaroko Yamamoto, a Gerenal (I think?): "I can run wild for six months … after that, I have no expectation of success." They needed the time to solidify their gains, but no such time was afforded them.
EDIT: *Admiral
The japaneese probably didnt expect the americans to laydown and surrender. Their plan was to invade all the pacific islands and build up an defensive wall against any american retaliation and make it so difficult for the americans to push them back that it would cost the US unacceptable casualties.
With the american threat somewhat "contained" they would proceed with pushing south and west towards australia. If they succeed the japanise would have the materials they needed for a full out war along side the germans.
This was a crazy dream, all the Japs could do was delay the Americans.
Before Pearl Harbor over 70% of americans was for neutrality, after... America cried out for vengance.
The japanese failed on two critical points at Pearl, they didnt knock out the US carrier fleet and they didnt destroy the fuel reserve at the docks