I often shoot cityscapes from a high elevation and tilts usually don't help, because you are typically dealing with perpendicular surfaces like tall buildings and the ground. Occasionally I've used a little front swing for that kind of shot, if there are two or three prominent buildings in the foreground in a line at an oblique angle to the horizon or if there is a receeding shoreline. Try setting up the camera square, using only front or rear rise/fall for framing and stopping for adequate DOF. Try at f:16, 22, and 32 and see what's sharpest.

A heavier tripod and head will often make a real difference. You might consider sandbags on the front standard to dampen and prevent transmission of vibrations from the shutter if you really want to maximize sharpness. Be sure your cable release is slack.

If you are on a rooftop or balcony, be sure to shield the camera from the wind.

As the others have said, for objects in the distance, there really is no substitute for a clear day.

Tech Pan in Technidol isn't a bad idea and is available in 4x5". It has some extended red sensitivity, so it responds well to red and orange filtration to cut through haze.

Use a compendium shade to restrict the image cirlcle to the minimum necessary to reduce both lens flare and bellows flare and maximize contrast.