The Brooklyn Brewery is located at 79 North 11th Street in Williamsburg, Brooklyn, 11249 between Berry Street and Wythe Avenue. Here's a map.
From Manhattan by Subway
Take any Uptown/Downtown line to 14th Street, change to the L train for Brooklyn, exit first stop in Brooklyn, Bedford Avenue (stay at rear of train), walk from North 7th Street to North 11th Street, turn left (towards the water) and walk a block and a half to the brewery.
From Queens, Long Island, Points North
By car: From RFK Bridge, Grand Central Parkway or Long Island Expressway, take Brooklyn-Queens Expressway toward Verrazano Narrows Bridge, after passing over Kosciusko Bridge (over Newtown Creek) take second exit for Metropolitan Avenue, turn right onto North 8th Street, go seven blocks, turn right onto Kent Avenue, then right onto North 11th, go a block and a half to the brewery.
By subway: G train to Nassau Avenue, follow Nassau until it becomes Berry Street, at North 11th Street, turn right, walk a half block to brewery.
From Manhattan by Car
Hard right turn onto Broadway from first exit on Williamsburg Bridge (you must stay in far right lane), follow Broadway past Peter Luger's to Kent Avenue, turn right onto Kent and travel about a mile, turn right onto North 11th Street, go one block, brewery on left.
From Staten Island & Points South
By car: Take Brooklyn-Queens Expressway to Metropolitan Avenue/Williamsburg Bridge exit, go to second stoplight, turn left onto Union Avenue (under BQE), after second light turn left onto North 10th Street, go six blocks to Kent Avenue, turn right onto Kent, then turn right onto North 11th, go one block and a half to the brewery.
From Downtown Brooklyn by subway: G train to Nassau Avenue, follow Nassau until it becomes Berry Street, at North 11th Street, turn right, walk a half block to brewery.
From Anywhere by the East River Ferry
Take the East River Ferry to North 6th Street/North Williamsburg. Walk up North 6th and turn left on Wythe Avenue until you get to North 11th Street. Turn right and The Brewery will be on your left side.