Clash of Clans - Getting Started

First Timers - Don't worry, your buildings will come back. You don't have to worry about actually losing anything structural - only gold and elixir. When you log back onto the game, you'll see that you've been attacked, lots of buildings will be in ruin, and in about 20 seconds, they will have "powered back up" and you're off and running again.
Watch your grid - After you place an item on the screen, you'll see a highlighted area around your village. This is an area the enemy cannot start within so be sure you don't leave any holes by placing structures too far apart.
The edge won't save you - Buidling your village close the edge of the screen doesn't stop attackers from starting in the surrounding green area. You still have to defend from all directions.
Huddle - Build your village close together to take advantage of keeping all things under protection of your weapons. Ensure that you have different types of weapons covering each other in case you're attacked from the ground or the air (e.g., canon = ground, air defense = air, and archers = both.)

Power in numbers - Once you've rebuilt your clan castle and joined a clan, be sure to fill it by requesting troop donations before you log off. While soilders in your army camps are only good for attacking, the troops in the clan castle can also defend your village. When you select the clan castle, you'll see a threshold radius appear (much like with other weapons) that shows you when those troops will be deployed. Take advantage of the extra troops for defense. It's one of the big benefits in being in a good clan.
Sacrafice the Town Hall - If you've already got your third builder and you're not part of one of the top clans, you're probably not that concerned with trophies and are more interested in farming for gold and elixir. By placing the Town Hall outside of your walls you'll make it enticing for attackers to go after it. When they destroy it, it will give them an automatic victory with one star. It will also give you an automatic shield. Your goal here is to protect the gold and elixir storage and not worry about wins and losses. Once you've built a killer base, you can worry about going for the trophies.
40% destroyed is 100% good - Place non gold and elixir holding (storage, mines, and pumps) outside your walls to allow them to be destroyed. Much like destroying the Town Hall, if the attacker destroys 40% of your buildings, you'll get a longer shield without actually giving up any resources.

Train your next army - Before you log off, fill up your army camps with an attacking army. The game used to kill those troops if the base was destroyed during an attack but now they will all survive the attack. You might as well invest as much elixir into a usable set of troops as you can.
Stock up - Also, once your camps are full, train as many wallbreakers as you can in each barrack. While they're not the most expensive, they are the most expensive per housing space (i.e., level 5 wallbreaker = 3,000 for 1 housing space so 3k/space and a level 3 P.E.K.K.A = 50,000 for 25 housing spaces, so 2k/space.) This will take elixir out of play for raiding armies who can only go after your pumps and storage. You can untrain them when you return to get the borrowed elixir back in your storages to spend elsewhere.