Avoiding creases when applying smoothing groups to
holes/non-quads?

I'm poly modeling (without meshsmooth/turbosmooth) and am running into major
problems when trying to cut holes into surfaces.

As depicted in the attached file (PNG image), if I cut a simple hole in the face
of a cylinder by removing some of the quad faces, I'm left with creases along
the edge faces, despite all faces being perfectly planar.

The problem is made worse if I decide to create a couple triangular faces in the
corner, thus making certain quads into N-gons. The creases become ev
en worse, although all faces are still perfectly planar!

How exactly does one poly model shapes with holes cut into the surface if
creases immedaitely appear, and only get worse as additional articulation is
added? This is a very simple technique-- I'm directly creating the final mesh
(like I said, no smoothing modifiers), and I'm working entirely with planar
faces, and yet I find the creases thus far inescapable.