Optimizing Images for Page Speed
It's always good to start with your images. I advise you download your blogs images and go through them one by one making sure that firstly if they display at a certain size (for example, 100px) on your blog that the actual image is that size. In your image editor open the image and check the image dimensions to find out if it needs fixing.
You also need to consider image compression. I like to use a tool called "Save for Web" in Adobe Photoshop. This tool allows you to see what different kinds of compression will do to an image visually and also allows you to see the final
file size before saving. This way you can find the smallest file size with the
best quality. If you do not own Photoshop then I suggest that you JPEG files
with a Medium compression. You can play with the compression levels to get
acceptable quality for your website.
Optimizing Wordpress Code and Plugins
That you do not use. Finally I suggest you take a look at your style.css file and if you have the knowledge go through and remove any code that is not needed. Often if you have made tweaks to your site you will find extra code here.