Maps
Here we give you some strategies in a simple form because YOU modify it YOUR way.
Seatown - The best strategy for this map is to camp in the South-East part of the map or the South-West part. Set up some claymores or Betties and aim out the windows and just roast some marshmallows if you know what I mean.
Dome - Stay in the big building and come out every now and then to shoot people because on this map, you will get owned if you stay outside. Camping won't get you much kills but if you want to maintain a good KDR, stay in the building and just peek out every few seconds. This strategy takes a lot of patience and can sometimes pay off.
Arkaden - Stick with teammates and you'll be okay. Camping isn't too good but if you do it, hang out in the Fast Food Counter.
Bakaara - Go to the small house south of the crashed helicopter and set up a claymore and a Trophy. If you camp here, you'll get a MOAB for sure. You have to be careful though. Once your Claymore is gone, you'll be gone if you don't check the stairs.
Resistance - Stick on the edges of the map looking inside. Be more careful though when you come across the stairs between the two roads of death. We use that term because you'll die if you go through them.
Downturn - Here you should camp in the Northern building. Use a mix between the strategies used in Bakaara and in Dome.
Bootleg - You're better of revolving around the map here. There are not very many good strategies here but we can say, be as cautious as a snake when you're on the road.
Carbon - Camp in the Central building and do not forget to set up a claymore near the entrance. Best to use the same strategy as in Dome.
Hardhat - Again, here you should revolve around the map because the action revolves around the map as well. Stay behind the action and move around the map slowly. Once you get the chance, throw a couple of grenades into the central area as well for some sexy multikills.
Lockdown - For a third time, revolve around this map too but this time much much faster and in a counter-clockwise direction. We have gotten over 15 MOAB's in the second month of Modern Warfare 3's release using this strategy.
Village - Camp in the caves for one half of the match, and revolve for the other half.
Fallen - Camp in the Western Building, set up a claymore, and shoot out the window or if you want you can shoot at the wall hoping to kill a bug. This won't get you a MOAB but it will keep up your KDR.
Outpost - Camp in the hangar. If an enemy comes your way, you can Spray n' Pray or you can try to kill the person. Your choice.
Interchange - Here you should stay in the east and use the same strategy as in Fallen. If you want to get a MOAB, you better Spray n' Pray that you'll get one but let's be realistic.
Underground - Stay in the Northern part of the map and camp there. We've gotten between 25 and 50 MOABS in around 150 games doing this but use a Silenced Type-95 with a Heartbeat Sensor.
Mission - Can you guess? Revolve! Revolve! Revolve! Revolve in a Counter-clockwise direction. Keep an eye out when on the road and when near the ditch. Snipers and Campers are everywhere. Especially on Kill Confirmed, Search and Destroy, and Domination.
DLC
Aground - This is a Snipers nest. There are snipers everywhere and if you can't beat them (which you probably won't) join them. You should snipe on this map and don't be afraid to Hardscope. Do not EVER let people put you down because you hardscope. It's what snipers are meant for, so use them however you want to.
Oasis - Revolve! Revolve! Revolve! Revolve! Revolve! Did we mention that you should REVOLVE? Revolving is an amazing strategy! Don't ask why we use it so much, See for yourself!
Lookout - Lookout because we got another Camping map! Camp near the Delta Spawns and pray you won't get found.
Foundation - Camp in the Northern part of the map. Remember that Camping is a strategy. Not a Noob move.
Getaway - Patrol the bushes. It'll guarantee you at least a 10 Killstreak.
Sanctuary - Camp in the Balcony. It's gotten us around 15 MOABS already.
Erosion - This is Revolve Heaven. If you live to revolve around maps, then you'll love this map. Revolve in a Counter-Clockwise direction and you'll be good.
Liberation - Camp in the East side of the Map. It should get you some kills and a good KDR but don't be so sure that you'll get a MOAB or a huge 18 killstreak.
Piazza - Patrol the Eastern part of the map. Patrolling is another awesome strategy. It can get you a MOAB if you're skilled enough.
Overwatch - Cue the Troll song because, we just gave you another Revolving Map! Troll-ol-ol-ol-ol!
Blackbox - This one is quite simple. Camp at the North-West building. Don't forget your snares because you just might catch an unlucky soldier with that familiar Claymore Click.