Memorial map, to me, works a bit differently than the other maps. It is the hardest one to see your competitors because of the dark textures and low lighting in places. Snipers often love this map because they can make long range kills without being seen. A popular sniping spot is all the way at the back of the map down the big hallway. You can almost always find someone crouching behind one of the fire barrels in the back looking through a scope. My advice:
1) Similar to other maps, never sit still, particularly in this map. You will get sniped a lot.
2) If you spawn in one of the "cubby holes" along the ledge on the edge of the map, run away immediately - you are a VERY visible target in these.
3) A good technique in Memorial is to use an assult rifle and randomly aim down your sights (ADS) in open areas and corners a lot. Your ADS will pick up on people that you may not initially see with your eyes because they blended in with the background.
4) Some people insist on climbing the short ladders to get up into one of the towers in the middle of the level. More often than not, you just become a target. Be silenced if you are going to play "that" game.
5) I find I am more successful when I keep to the outside running lanes of this map, occasionally going up and over hills. Cutting across the middle seems to put you smack in the middle of a multi-enemy fire fight.