I normally set up my scopes this way, if the scope rail doesn't have 20 or 25 MOA tilt...
Using either adjustable rings or shims (the Hawke 25 MOA shims are great), I set the scope so that it is near the bottom of the elevation travel. So if a scope like the Athlon Ares or Midas mentioned above has about 2 1/2 turns bottom to top, I'll zero the scope at 50 yards so that I am 1/2 to 3/4 turn from the bottom. This is far enough to not hinder clarity, but low enough to give you lots of upward travel. For example, with the Midas TAC on my Eddy R3 Long shooting slugs, I can dial up about 300 yards from a 50 yard zero.
For scopes like the Hawke Sidewinders, that have about 5 or 6 turns total on the elevation turret, I set the scope at 1.5 full turns from the bottom. This still gives me plenty of overhead to dial up longer shots.
Hawke 25 MOA shims - If these shims are not wide enough, grind off the forward lip of each one and they will then fit any scope rings. Since they come in a set of rear and front shims they do not stress your scope tube like just shimming the rear.