If you plan things right, then you can be present for any one of the special 150th anniversary events or battle reenactments scheduled during 2013, and relive the Battle at Gettysburg. But if not, thousands of soldiers converge upon Gettysburg annually in July to re-create the bloodiest battle on American soil. Plus, if you visit town anytime on the weekends between April and October, you're likely to catch Civil War reenactors camping out on various lawns and fields.
Anniversary or not, Gettysburg is hard to conquer in a day. Once you get started, you may even think that three days is not enough. However, since the Union was able to defeat the Confederacy in three days, you can conquer Gettysburg in that much time as well. 
Military men taking a break on the campsite — Photo courtesy of T. Browne Smith
Day 1
Come in on a Friday morning and start your Gettysburg experience at the Gettysburg National Military Park Museum & Visitors Center to get your bearings. Before you hit the Battlefield or visit any of the camps you spot around town, you'll want to have a sound basis for what you're witnessing.
The Museum & Visitors Center will start you off with the enlightening and moving "A New Birth of Freedom" movie, produced by The History Channel and narrated by Morgan Freeman. Equipped with that general knowledge, you can tour the museum and look through its Civil War exhibits prior to heading upstairs to the Gettysburg Cyclorama. Complete with lighting and sound effects, this 50-feet-high, 400-feet-long panoramic painting, in a cyclical dome, literally puts you in the middle of the battle.
In the afternoon, visit a few of the most popular historic sites in town. Re-trace Lincoln's footsteps and visit the Historic Railroad Station. This station doubles as a Visitors Center for the Gettysburg Convention and Visitors Bureau. After gathering some other itinerary ideas, head to the David Willis House, where Lincoln slept and put the finishing touches on his Gettysburg Address. You might acquire some profound inspiration of your own as you walk through the home. Lastly, head to the Soldier's National Cemetery, where Lincoln delivered his Address and where 3500 Union soldiers are interred. 
Lincoln at the Hall of Presidents — Photo courtesy of T. Browne Smith
Day 2
Begin the day early with a tour of the Battlefield. For a more interactive experience, take the tour via Segway or horseback with a registered Battlefield tour guide. Along the way, you'll bump into reenactment camps. If your guide is nice (and flexible), then he or she will let you dismount and interact with the camp residents. Here, you can see collected artifacts, period furnishings and what life was like in the 1860s. 
On a Segway tour of the Battlefield — Photo courtesy of T. Browne Smith
Remember where you stopped so that you can return once your guided tour resumes. Your guide will more than likely allow only 10 minutes to stop. Then, once your tour is done and after you've grabbed a bite to eat, return to the reenactment camp you saw along your tour. These camps vary in location so you'll just have to keep a look out.
One location where you can count on catching a tour is the American Civil War Wax Museum on Steinwher Avenue. Reenactors are usually there on weekends. 
Reenactor camp outside Civil War Museum — Photo courtesy of T. Browne Smith
Day 3
Hopefully, you haven't hit your Civil War wall and you don't mind heading over to the Battlefield by car to find another camp. Drive along the trail and you'll surely run into at least two more camps. You can also head over to the Seminary Ridge Museum, where encampments are popular. No two are alike: they all have their unique appeal.
Spend a relaxed day here, learning, interacting, watching drills and demonstrations and asking questions. If you're nice enough, you may even get a bit of Civil War era grub to eat. 
Inside the tent of a reenactor — Photo courtesy of T. Browne Smith