You're referring to incidence.

You can go either way, but the flying characteristics of the plane will depend on the relative incidence between the main wing, the horizontal stab, and the fuselage (don't forget the fuse produces some lift and drag).

For a symmetrical airfoil, if you mount the wing parallel to the fuselage centerline, then in order to fly straight and level, your fuselage, along with the wing, will be angled up. Obviously, the fuselage is not as efficient (Lift/Drag) as the wing, so this will result in an implicit drag penalty during normal flight. So, you might consider adding a couple of degrees of wing incidence (relative to your fuse). However, if you plan on flying inverted a lot with the plane, you might want to keep the incidence at zero, so things will be the same right-side-up or inverted.

In general, you want your horizontal stab at the same level or below your main wing incidence (assuming both are symmetrical). For example, if your wing is at 0 deg., your stab can be -2 deg. to 0 deg. If your wing is at +2 deg., your stab can be at 0 to +2 deg. This is true for most aircraft with a traditional setup, as the stab typically produces a bit of negative lift as the plane is flying straight and level; this setup simply biases everything that way to help with neutral trim. Again, the exception would be if you planned on flying inverted a lot, in which case you might want to keep everything at zero incidence.