This is bit incoherent rambling type page, but it has some good info while its not a tutorial by any means.
How do you setup your random missions, here are some issues, solutions and thoughts etc.
class names is used to extract location data from the terrain config to be used in mission.
All terrains should have class names setup (locations), but some idiot modders do not include them. Then there are of course the very rare cases which do not have any location names, like desert_e in Operation Arrowhead, but I don't really think many people are doing missions for it anyways.
class CenterPosition is used to extract terrain's center location (ie size) location data from the terrain config to be used in mission.
CenterPosition should be what it says, center position of the terrain.
All terrains have this but it is no way certain that it actually is the center position, many modders just leave it to what ever they copy pasted the config or put it to some “nice” location on terrain.
If you rely on getting information from class names or class centerposition, then you might run out of luck very quickly. If terrain has been configured properly with both of these then great, you're all set for easy mission making, however as said often the case either one of these is unusable due class names missing or centerposition in totally wrong coordinates.
Place playable units and respawn_ markers into top-right corner which is the furthest place in the terrain.
Then use scripts to determine the terrain area by looking the player coordinates as the maximum coordinates.
Place playable units and respawn_ markers into lower left corner close to [0,0,0] position.
Then use script <ctrlMapAnimAdd> system to get terrain area. Check out arma2 missions find terrain size page for details.