Defending in Clash of Clans basically comes down to two things, the strength of your defensive structures, and your base layout. Once you unlock the Clan Castle, you are also able to store troops in there who are triggered, once an enemy gets close enough, to help defend your base.
Defensive structures can be things like Walls, to protect buildings and direct enemies, as well as more physical deterrents so as Cannons and Mortars. You are also able to place traps, such as Bombs, which activate when an enemy unit steps on them.
These go hand-in-hand with your base's layout, as you ideally want to channel enemies down a certain path into the best defended area. Once an enemy places their units, there is nothing they can do to change the path that they take. This means that if you learn how the AI works in Clash of Clans, you can predict where enemy units will end up.
TIP: YouTube base designs to find the best bases in the game. Check out Halo Okraheads Clash of Clans for more informative videos!
Worthless article.
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Will Rathaus level 10
Thanks for the constructive feedback, and yes there is a base layouts page which is here: http://www.supercheats.com/clash-of-clans/walkthrough/base-layouts
To add a slight apology to my earlier post - there is a section called 'Base Layouts' which does deal with this topic in more detail :-)
While I agree that the guide is trying to be helpful - it actually isn't. It basically says you need to learn the enemy AI by yourself and then work out a defense strategy by yourself because there are so many options. Instead of just posting a random picture of a base layout, why not explain what's good/bad about that layout? It would be a nice idea to post an example of a bad layout and explain why it's bad. Then post a pic of a good layout and explain why it's good. Good intentions only get you so far in a user guide - it actually needs to be useful. In saying that, I do appreciate the effort :-)
You should tell people HOW to make a good layout in detail.