Level Design necessities-

All Modeler's -

-before exporting your asset as a .fbx-

Check your face Normals to see if you don't have any inside out faces so your assets will render properly inside of UDK. (BackFace Culling)

Continue to upload your assets into the custom assets folder of the repository.

Textures must be! 256 x 256 -UNLESS- it's for a character -OR- you have created a large part of the building itself.

Textures must be in the .PNG file type