There are 2 aspects you should think about if you would like to speed up your site: optimize server side by improving server performance and optimize client side by reducing loading time but still keep user experience. These steps are not only make your visitors/customers happier but also increase quality score and improve Google ranking of your site.
With WordPress, there are some (or even a lot) plugins can help to speed up your website/blog but I just want introduce 2 plugins that most popular: WP Super Cache and W3 Total Cache.
From my personal, I’m using WP Super Cache in my blog because it’s simple then W3 Total Cache or maybe because I am not familiar with it
Below is my settings in WP Super Cache CDN:
Bonus: before and after optimizing your site, you should use An Online Test Website Loading Speed Tool to see how’s your optimization job going.