Magento is quite a resource intensive program which can benefit greatly through various methods of optimisation. Outlined below are various techniques that can be used to speed things up.
Enable all of the caching in the Magento Admin area. By going to the System -> Cache Management area of Magento you can enable various caches. Enabling these will cause Magento to start caching various files and settings locally to avoid browsers continuously requesting the same data over and over when you access a new page. This in turn will reduce the page load time for your website.
Enable the Flat Catalog option in the Magento admin area. This is mainly aimed at larger Magento sites that have a large number of entries in the database. To enable this do the following:
Navigate to System -> Configuration menu and click on the Catalog option and then select the Frontend tab. Choose Yes next to the appropriate selection of either Use Flat Catalog Category or Product. Note: If you want to use only Flat Category there is no need to enable Flat Product.
For VPS or Dedicated Server customers:
A VPS or Dedicated Server should always give you better performance with a Magento site. This is down to the fact that you will have more resources, RAM and CPU available exclusively for your Magento site to utilise.
Enabling APC or Varnish caching on your Server. We are able to install advanced caching programs on (virtual) dedicated servers, the most popular programs being APC and Varnish. We are able to configure on your server to further improve page load times for your websites.
In addition to installing Varnish on your server you will also need to install a Varnish plugin to fully take advantage of using Varnish on your server. One such plugin is called Turpentine. We can help you configure this plugin to further improve load times on your website.
Generally speaking it is also worth checking the page sizes for your websites with a tool like Pingdom's. While caching and server optimisation can go a long way to improving page load times, if you have a 10MB front page of a website you will always find that your website will always load slowly. In most cases large page sizes will be due to a lot of images/large images or perhaps video files on your website. Reducing image sizes can go a very long way to speeding up page load times on your websites.