The first stop on a visit to Gettysburg National Military Park should be the park visitor center. Here you will find the usual maps, tour guide info, ranger led programs info, giftshop/bookstore, and an incredible Civil War museum. Here you will find the largest Civil War collection in the National Park Service with more than 40,000 artifacts.
The museum contains exhibits which portray the living conditions and daily life of a Civil War soldier. You will view the living quarters (tents) of both enlisted men and officers, which shows the officer's "upgraded amenities". In these camps you will see personal items such as bedding, dishes, and writing desks in the officer's tents; items for "battling boredom" such as playing cards, chess boards, poker chips, dominos, etc. There is also a nice display of soldier (both Union and Confederate) uniforms, clothing, and personal effects.
The museum also contains photos, portraits, flags, battle relics, and more weapons than I have ever seen in one place. The weapon collection is incredible! Along with the objects in the museum, there is also very much information describing the war - from everyday life to an exhibit pertaining to two brothers fighting against each other on opposite sides. There is also a wall with photos and information about some of the soldiers who fought in the war.
There is much to see at this museum, and you should plan on spending at least one to two hours if you want to view all of the exhibits. The website for further information is here. The website for Gettysburg National Park is here. The visitor center/museum hours are 8am - 5pm. Summer hours are 8am - 6pm (subject to change).