Choose the right hosting, use a fast server.
Use a content delivery network for serving static files from the closest possible place.
Use a caching plugin to store the static content so that it doesn’t load every time an user visits your blog.
Use small pictures (scaled images) and upload them as small files instead of having them compressed by WordPress.
Remove unnecessary plugins and keep existing ones updated.
Use CSS sprites (combining multiple images into a single file containing all information of all the graphical elements in it)
Use as little dynamic content as possible.
Move your scripts from your header to your footer.
Repair, optimize and back up databases regularly.
Reduce the number of external calls or requests that your site makes.
Use compression like Gzip.