For the real flavor of what horrors could be experienced in trench warfare, The Trench of Death is the place to see.
The town of Diksmuide is interesting in itself, even though it was bombed during the war and rebuilt. The statue in the picture is in the large main square. Don't miss the Blankaart Nature Preserve if you're a nature lover. It's just south of town.
The link goes to an introduction to the Flanders Fields Museum which gives you a pretty good idea of the Ypres of today, which was totally demolished during WWI and rebuilt. Besides the Museum, there's the Menin Gate Memorial, Sanctuary Wood and Hill 62 to visit.
Every evening at 8pm, the Last Post, the traditional bugle salute to the fallen warrior, is played under Ypres' Menin Gate Memorial.
Ypres has a train station (Ieper). Bicycles can be rented at the station, where you'll also find taxis.
The Lille Tourist office has announced a new WWI remembrance tour startings on April 4, 2010. Covered are memorials, battlefields and cemeteries in the Fromelles and the Weppes area.
The Battle of Fromelles was the first important battle on the western front involving Australian troops. It is also considered to be the bloodiest 24 hours in Australian military history.
You can also download free audio tours of Somme, and Circuit of Remembrance. One of the largest battles of the first world war took place in the Somme.
If you're on vacation in Paris and are looking to get out of town for a little different view of WWI battlefields, this Viator tour might just suite you.
"On this small group tour of the Somme battlefields, you will discover a part of France that suffered severely in the violent and bloody battles of the Great War. A dramatic period of history took place here, and you will see the major sites including memorials, cemeteries and traces of battles. Numbers are limited to a maximum of 19 people, ensuring you'll receive personalized attention from your knowledgeable guide."