A slow loading blog can prevent you from getting new readers and it can also adversely affect your Google rankings. If you notice your blog loading too slowly, or just want to optimize the speed there are a few things you can do.
1. Use a free web analyzer to determine where your bottlenecks are.
A couple good sites for this are Pingdom and GTMetrix. These will test your site speed and list out all your elements so you can see which ones are taking the longest to load. From there you can decide how to improve your speed.
This doesn't actually make your blog load any faster, but it gives the illusion of it because browsers cannot load any other elements such as images at the same time as a script. So moving them to the bottom allows your other elements to load and render on screen first making the user think your site is faster.
To do this, go to Design > Edit HTML and place your scripts just before the closing </body> tag in your template. Or place your scripts in a widget at the bottom of your footer.
3. Reduce the amount of posts in your Home Page.
This one is important especially if your posts are image intensive and you don't use Jump Breaks to separate your posts.
Go to Design > Page Elements > Edit your Blog Posts to change the number of posts.
4. Reduce your image sizes.
The most common ways to do this are to save your images with a lower quality; or crop and scale them down to the exact size you want displayed on your blog with Photoshop instead of scaling them with HTML.
You can also use this handy web tool Yahoo! Smush.it to further optimize your images.
5. Reduce the amount of gadgets/widgets
Gadgets and widgets offer cool features to enhance your blog but having too many of them can slow your blog down to a crawl. This is true especially if you are using third party widgets. Sometimes these use scripts and code that are hosted on slow servers. Check them in a web analyzer to see if they are holding your site up.