Take the J, M, or Q trains to DeKalb Avenue and walk down the hill. You can also get to downtown Brooklyn on the 2, 3, 4, or 5, which converge at Nevins Street. Upon exiting at Nevins, turn left and walk a block or two down Flatbush to DeKalb. Go right and down the hill. Tillie's is at the corner of Vanderbilt and DeKalb about ten blocks from the DeKalb stop. There are also gypsy cabs available on Flatbush Avenue after you exit the subway.
Take the C to Lafayette, then walk down Lafayette to Vanderbilt, where you turn left and go one block. Or take the A to Hoyt/Schermerhorn and switch to the G directly across the platform, exiting two stops later at Clinton/Washington.
From Manhattan take the Brooklyn Bridge and turn left onto Tillary. Go straight and then under the BQE along Park Avenue to Vanderbilt. Turn right and go four blocks to DeKalb. Or take the Manhattan Bridge and head down the Flatbush extension straight off the bridge. Turn left onto Myrtle to Vanderbilt, then turn right and go up two blocks.
From Queens and other points north and east:
Exit the BQE at Kent/Wythe, the first exit after the road splits beyond the exit for the Williamsburg Bridge. Take the service road to Flushing Avenue, along the Navy Yard. Turn right onto Flushing to Vanderbilt. Then turn left and go several blocks to the corner of Vanderbilt and DeKalb.