Optimisations Tips
Install A Cache
This is an absolute must. If you’re not already using a caching plugin and you’re complaining about page speed install a caching plugin immediately! I recommend WP Super Cache or W3 Total Cache.
Optimise Images
Optimising your images reduces their file size without losing picture quality. You can either use a program that does this before uploading your images to your server (such as ImageOptim for the Mac) or you can use a WordPress plugin that does this after uploading your images.
Minify HTML, JavaScript & CSS Files
Minifying your JavaScript and CSS files basically makes these files as small as possible so they load quicker. There are plenty of plugins out there that minify these files, I recommend Autoptimize.
Remove Query Strings From Static Resources
Use the following Remove Query Strings From Static Resources plugin to remove query strings from static resources like CSS and JavaScript files, to improve your speed scores in services like PageSpeed, YSlow, Pingdom and GTmetrix. Resources with a “?” or “&” in the URL are not cached by some proxy caching servers and moving the query string and encode the parameters into the URL will increase your WordPress site performance.
Cache Gravatars
By default the Gravatar icons are loaded from the Gravatar server, you can cache these and host them from your own server to reduce page load time using the Optimum Gravatar Cache plugin.
Using A CDN
You can use a Content Delivery Network (CDN) to host your files (images, JavaScript and CSS files). This works by providing alternative server nodes for users to download your files. These nodes are spread throughout the world so they can be geographically closer to your users, ensuring a faster response and download time of content due to reduced latency. Some of the most popular CDNs are Amazon S3, Microsoft Windows Azure and MaxCDN.
My Site Is Still Slow
Query Monitor
Install the Query Monitor plugin to see if there are any database queries that are slowing down your site.
Plugins
Having multiple plugins installed and activated on your site can slow it down. The more plugins you use, the slower it will be. Please disable all the plugins on your site except for those required by the theme.
Now clear your browser cache and see if it speeds it your site up. If it does activate the plugins one by one and check the site speed each time to try and find out if a specific plugin is causing the slow down.
Unfortunately there are plugins out there that can slow down your site, if you happen to find one please contact the plugin developer and report it to them.
Server/Hosting
If you site is running slow and you are hosted on a shared server you should consider moving to a VPS or dedicated server. A shared server distributes the server resources across many sites leading to a noticeable slow down when sites on the server have a lot of visitors. If your own site is getting a decent number of visitors you should definitely not be using a shared server. With VPS and dedicated servers you have your own server resources that are not used by any other sites.
Even if you are using a VPS or dedicated server, some web hosts are better than others. Speak to your web host about increasing your server specifications or consider moving to a different host. I recommend WPEngine.