Clans
Clans consist of players that are joined under the same banner. Clanmates can help with building structures around your base, sending units over when you get attacked, etc. There is no cost to join a clan. However creating your own coin costs thousand gold.
Tasks
Tap the rolled scroll at the top left corner to display the tasks window. Tasks are passive quests. Each of them has a timer. Simply wait until that timer expires then collect the rewards. There are three types of tasks: personal, clan, and premium. Personal tasks reward you with resources and general items. Clan tasks are similar, but also give additional bonuses for your clan. Premium tasks are rare, and usually can only be active one at a time. When completed, they will reward you with gold and premium items. There is also a cooldown of a few hours before you can select another premium task. Always try to have a task running.
Various General Tips
You can only teleport to another kingdom until you reach Palace level 6. In order to do so, click on the world map, choose a kingdom, and then find an empty tile.
The chief of the clan that holds the Place of Power is the Konung, or the ruler of the kingdom. Place of Power is located in the very center of your kingdom and you can attain it by attacking and defeating the current Konung, then defending the PoP for six hours.
The Konung receives a daily bonus of 10% of the silver from every clan chief in his kingdom, and also 20,000 prowess pints. The Konung can also place up to 16 positive and negative buffs to Jarls in his kingdom.
Look for the kingdoms that have resources but zero troops as they are usually run by players who have stopped playing the game and are therefore ripe for the taking.
Clans...