Major & Mrs Holt's "Ypres Salient" book & map
Clothing/Shoes/Weather Gear: Waterproof Jacket and hat!
Miscellaneous: If you are interested in the four WW1 battles and want to visit Ypres/Ieper and the Salient, a "must have" is Major & Mrs Holt's Ypres Salient book (isbn 0 85052 551 9). It's about £15 but worth it and it comes with a map marked with all the "sights"
Clothing/Shoes/Weather Gear: Good walking shoes are so important. Its cobblestones, cobblestones and cobblestones. Everywhere.
Of course you are in Belgium and wet weather gear maybe needed.
Photo Equipment: Bring plenty of film, or memory cards for the digital.