An effective strategy to ensure you have a chance of gaining a victory against a rival community is to send out a scout to their base to find out what you will be facing when you get there. To send a scout tap an enemy base and select the 'Scout' option, this will despatch the scout from your base who will note the number, strength, and class of defenders and any garrisons deployed to protect this base. The scout will also record the resources the enemy camp have on hand to loot before it returns home.
Remember though when you send out a scout it will take up one of your raiding parties even though all your troops remain home and there is also no element of surprise as your target will be notified of your intentions.