How do you scout another camp?

When you scout another player you will send a helicopter to their base. When it returns you will have a message (in the mail option, under battle reports) wit the result of the scout. This will give you information about their base, You can't see in the base unfortunately.

The quality of information will depend on the level of your radar building, but it will give you an idea of the amount of troops they have and the amounts of resources for raiding.