There is a simple and effective way to help speed up your Joomla site. It is called "caching". When you use the caching feature, Joomla creates a static file (or cache), of your web pages. This means that your website can use this cached file instead of making redundant database calls each time someone goes to a page. This in turn saves time and speeds up your site.
Log into the back of your Joomla site (/administrator) to turn caching on. Go to "Global Configuration" as seen below.
Next, click the "System" tab. On the right side of the screen you will see the caching options:
All you need to do next is turn the cache on. The "Cache Time" is how much time will be delayed between refreshing the cached webpages. Keep it at 10 minutes if you don't have any preference.
Once caching is enabled, you may also want to turn caching on for your modules (assuming they have this feature, and unfortuantly many do not). Many modules use database queries to retrieve data, such as a module that displays the latest forum posts of a message board.
Click, "Module Manager" in the "Extension"drop down menu to get a list of all your modules.
Click the name of the module you would like to turn caching on for (if the option is available). Turn caching on, and click "Save".
That's all there is to it.