On the Samsung Galaxy Note, you can use the S Pen to achieve the equivalent of a mouse hover, even though its on a touch screen device. Does the Surface (or any of the new touch screen windows 8 all-in-ones) have similar capabilities?
A "long" click seems to work on my Surface - at least on websites.
I place my finger where I want to hover (for example my name at the top of the screen) and hold it there for a couple of seconds. The flyout menu will then appear (along with a another popup as well).
I believe this is really supposed to simulate a "right click", but seems to work for some things - it doesn't let me up vote comments for example.
A hover action is simulated by a long press (tap-and-hold). However, that doesn't seem to work for all of my apps.
Digitizer pen input has long been supported in Windows. These easily support hovering the cursor. Without a pen, though, the best you have is either use a long press or a touchpad or mouse accessory (like the keyboard cover for the Surface).