CoD4 Overgrown is one of my favorite maps in the game. The map is very open and allows you to be creative. For server size I would recommend 12v12 on overgrown, after that it will start to feel clustered. I'll get you started with some general tips in this video and them break down parts of the map further in this article.
Prenading in CoD4 Overgrown
One of my favorite things about over grown is prenading doesn't work well here. You might get lucky and score a kill every once in a while with one. I will show you a few spots to try out, you are usually better off saving your nades for later in the round.
Line yourself up next to the stove.
Throw the nade over the hole in the wall.
Next Spot
Line yourself up with the building to the right
Throw your nade a little bit higher and to the right of the tree.
CoD4 Overgrown Key Map Routes
The most important part of any CoD4 map are the routes. Navigating the map so that you end up playing in a lot of one versus ones, instead of trying to fight the whole team yourself. I'll show you how to out maneuver and stay one step ahead of your enemies.
Middle This is the most important part of the map. You should be making more than a few trips through this area, every time you pick up a string of kills or run into too many enemies. Some times a sniper on the opposing team might shut down this route. Try throwing smoke to get through, if that doesn't work just take the long way around the map to get to him.
North Another key point in overgrown. It has 3 buildings that offer great cover. Being able to take control of these in DM and TDM will give you a huge boost in kills per round. Once you get a bunch of kills in this are you will have to move on to our next point of interest.
South South has two huge assets that can help you secure this part of the map. The mounted MG and the crack house (big house in the picture). You can easily pick up 2-3 kills creeping around in that house, then make your escape out the back into middle never to be seen again. Try not to spend too much time in the MG, good for clearing out the house which should be your objective.
CoD4 Overgrown Popular Spots
Different spots favor different loadouts. You have probably noticed that snipers usually flock to one area and assaults/SMGs to others. Knowing these patterns will give you an edge when navigating the map.
Sniper Spots About 90% of the time if you see a sniper on overgrown they will be in one of these spots. They were good spots in early CoD4, but not people are catching on. Save your grenades for these spots or take long routes to flank them, easy kills if you approach them correctly.
Assault Rifle Spots Mostly assaults in this map find a building to hole up in and play long range fights. They usually do this in every cod4 map, not just overgrown. Easy kills if you can back door them, as long as theres no UAV up they will probably be looking out the window.
SMG Spots These guys are usually all over the place in CoD4 overgrown. Since they move around so much expect to see them using routes across middle. Like Assaults they go from building to building but they focus on clearing out rooms instead of using the windows for range fighting. The most effective way to take down a good SMG is to pick them off with an assault rifle when they are moving from building to building.
CoD4 Overgrown - CoD4 Maps