In iOS 8, if you’d rather have the desktop version of a site in Safari, tap the
address bar smart search bar and request it. Just scroll down on your favorites that appear for the button.
This is also a quick way to add sites to your favorites, too.
Note that Apple is specific with the language of this feature, because not all sites will comply. Twitter, for example, forces me to mobile.twitter.com and won’t serve the desktop version no way no how.