Attacking
Scout before you attacking other players to get an idea of their resources and army. The level of your scouting ability will determine the accuracy of the scouting report. You can then decide whether it is worth attacking. However, the targeted player will know who scouted them and be able to retaliate.
Resources
Take note of the small money icon that represents the routine supply at the bottom left. It can be collected about every half hour for free resources. The rewards center will often send you rewards, which is indicated by the present icon at the left side.