Crash gets its name from the helicopter that is stranded in the middle of the village. Around the helicopter are several buildings and one particular building with three stories. You'll find lots of windows to snipe from as well as ladders to get to higher places.
There are three key places in the map. The first is the three story building. I call this, "three story". The marines can reach here faster than the terrorists at the start of the game. What people like to do is to plant claymores on the stairs, so take them slowly. Snipers often position themselves on the top of the floor, but sometimes, you'll find a few on the second floor. There are four entrances to this building, two from the bottom, one ladder right to the top and a stair to the second floor. It is recommended to take the second floor stair as you might sneak up on whoever is there. What's extremely useful to kill these snipers is grenades. Just aim high enough and throw one on the third story and you should be able to get a few. One thing to take note is that when an enemy helicopter is summoned, do not stay on the third floor. This building can also be used to get the Goodbye challenge just by jumping off it.
The second key place is the "blue building". This is the building that is close to where the terrorists start. There are three entrances to it. One is directly across the helicopter, the second faces the three story building and the third is closest to where the terrorists start. There is a set of stairs in this building and people like to snipe, facing the three story building. You might find claymores here, so proceed slowly. It may be helpful to throw a frag into the windows to take care of anybody here.
The last key place is directly across the blue building. This building has a market on the first floor, then a second story with several windows. There is also an open rooftop here and a ladder nearby. It is recommended to get here through the first floor. Taking the ladder always makes you slow, vulnerable and unable to fire. I call this the "shop".
There is a few other areas in the map that are minor. There is a two story building near the terrorists spawn, but it doesn't offer many advantages other than a hiding place. On the opposite corner of the map, there is a similar building to the marines, but again, it won't see much action.
There are some things to remember about the map. Like most maps, avoid the centre area. Enemies from all parts can see you easily. Try to run around the perimeter. There is a long hallway that borders the shop. Try to avoid running down here as much as possible. If you must, find some cover behind trash cans; otherwise you are easy prey. The two most popular buildings are often the three story, followed by the blue building. Airstrike here when possible.