Question:
Give a simple example of what, where and how to cache?
Answer:
What should be cached is something that takes a long time or requires a lot of computing resources, for example, image resizing, long queries to the database, and so on. There are many caching systems. You can use memcache and apc at the same time, but remember that they will eat resources together. Install the php5-memcache php-apc packages and use, for each of them the corresponding functions and classes are provided.