Following the 24 hour Preparation Day in Clan Wars, comes Battle Day. This is the day when clans can attack, start scoring stars and pushing towards victory. Remember, every clan member who makes a successful attack during a clan war will earn some bonus loot, but only the winning clan receives a large loot bonus.
During the Battle Day, there are two main activities: scout and attack enemy war bases. You can not rearrange your war base during this phase.
Each clan member is limited to just two attacks during Battle Day, so make sure you scout and clan chat to prepare your attacks in advance. You can choose to attack any opposing player, although you can't attack the same target with both attacks.
The main goal in attacking is to earn stars for your clan, so make sure you choose targets you can defeat. To help you select an enemy, you'll have a recommended target visible on the war map. This recommended target represents the closest match for your attack strength based on the defense strength of your opponents.
When attacking, only the "best attack" — the one that has scored the most stars against that base — will count towards the clan's total stars.
As a reminder, because your war base is separate from your village, you won't lose your shield or resources during a clan war. You also don't need to rearm your traps or reload your defenses; this is all done automatically.
The winning clan in a clan war is determined by the total stars earned by the clan. Stars are rewarded in the same way as in multiplayer matches: 1 star if you destroy a Town Hall, 1 star if you destroy at least 50% of the buildings in a base, and 1 star if you destroy 100%. However, only the "best attack" against each war base will count towards your total. This means, if someone has already earned 2 stars against an enemy base, you will have to earn a perfect 3 stars against that same base to add one additional star for your clan.
Winning a clan war will award you the full bonus loot accrued from victorious attacks as well as a new point in the "Wars won" stat, visible in your clan description. Members of a losing clan will suffer a stiff penalty to their bonus loot. You'll still be awarded bonus loot, but it will be heavily reduced. A clan war can end in a tie if both clans have the same number of stars at the end of Battle Day. If this happens, both will be awarded bonus loot, but at a penalty (not as heavy as a loss though).
Clan Wars still isn't implemented in Clash of Clans just yet, but in the meantime Supercell is hosting a 1 gem bonus special to help you prepare for war.