For those not familiar with the area or downtown Chicago, the Sears tower is located in the block bordered on the north by Adams St and the South by Jackson Blvd. It is bordered on the west by S Upper Wacker Dr and the east by Franklin Street.
Coming from the east, just walk west on either Jackson or Adams and you'll eventually hit it before hitting the river. It's the really tall building that's towering over everything else.
The lobby entrance for the office building is off of Wacker Drive, not Jackson Blvd. The skydeck entrance is on Jackson. Come up to Wacker and go in via the main entrance to get to the elevator bank for the Met Club.