Is your target of a lower level than you, and are they still active or have they left the game? What are the possible counter actions from your foe? Once you have gone through your decision making process and weighed the pros and cons, then you are ready to think about the best attack strategy to your target.
In Plarium MMO games, you will have raids on nearby fellow players, and you will also have in-game raid tasks to generate more units and rewards. Simply speaking, the former is to reduce the capability of your enemies, while the latter is to earn points and rewards to raise your playing level.
In most MMOs, raiding your local rivals is usually the easiest, and you can normally pick off non-playing or lower level players which will earn you valuable resources that you can then turn into new buildings, upgrades, or more units. However, the rewards for participating in raid tasks against non-player entities can be lucrative.
If you're struggling to find easy human targets, consider spending some time attacking NPC forces. But remember to keep your neighbors in check - a human player is always more dangerous than NPC enemies.
Raiding really boils down to how many troops you have and how far you can push them to gain more rewards to get more troops, so essentially it is just turnover to increase your size and power within your area of operations. If you raid well you will find yourself in a self-reinforcing cycle, as you can spend the spoils of raids on more troops which you can then use to raid more ambitious targets. But, if you overextend and find yourself defeated, the opposite cycle could happen as you struggle to recover the troop numbers you once had. Find the right balance of caution and bravery.
One thing is for certain: if you do not raid, you will never truly reach the levels required to dominate your area of operations within your game.