Sikhs can worship anywhere, so long as it contains the Guru Grath Sahib.
All visitors MUST cover their heads while in the main Gurdwara areas i.e.: (Darbar Sahib and Langar Hall)
All gurdwaras have a flagpole outside and a flag called the Nishan Sahib, containing the Khanda symbol. The flag is raised every after the flagpole has been taken down and washed. The old flag is thrown away.
Which room is used for eating in?
The first room you find in the Gurdwara is usually the shoe room.