Little Round Top, historically, was the most decisive and hardest-fought engagement of the battle. Your mission as the Union is to hold off the attacking Confederates as long as possible in the Devil's Den and in the Peach Orchard, while your reinforcements get situated on Little Round Top. Eventually, you are probably going to lose Devil's Den, so the question is how to make the Confederates pay the highest price for the ground traded. Here at Firaxis we like to shift Ward's brigade to the south, onto Big Round Top. This way, they can slow the Confederate progress on the trail that goes up the hill. Ward's infantry also takes less damage when protected by the woods and rocks. Move the artillery back to supporting positions on the hillocks, and make sure they don't get overrun after Ward's men are pushed back. After these guys are engaged, they should always be on "Fall Back", to avoid getting trampled by the large, experienced regiments of Law and Robertson. Once Vincent's brigade appears, immediately move him onto Little Round Top where he can dig in as Ward trades ground for time. Keep Ward's withdrawal orderly, as you'll want those guys later on in the scenario to plug gaps.
When playing as the Confederates, the trick is obviously to keep on plowing through the Union lines in the race for Little Round Top. If the Yankees try to hold Devil's Den, outflank them and set up a screening force while the rest of your army slips on by. It can be a slow and difficult process to advance up the Big Round Top, through all the woods and rocks, but it does give you covering fire from Union artillery and the advantage of stealth. If he moves onto the Round Top, exploit the gap created in his lines at the Devil's Den and push through on the other side. Once you get to Little Round Top, work your way around the flanks and hammer away. Keep a couple of regiments in reserve to deal with the small Union reinforcements (Cross and Kelly) that activate later on; also, if you can delay DeTrobriand with a few skirmishers, you'll have an easier time with Vincent.
