minimize orientation effects
Position gates for uni-directional flow, and modify part thickness.
change part geometry
Add features such as stiffening ribs to the design. Alter part design to avoid thick sections and reduce the thickness of any features that intersect with the main surface.
use thinner wall sections with ribs
Thicken only those wall sections that require extra material for structural stability and that cannot be strengthened using another method.
change material
Semi-crystalline have naturally higher shrinkage and hence are more prone to warpage.