Here is an awesome guide that I found on the official Kerbal Space Program Forums. You can view the original here.
It does a great job of explaining the different ways that a plane can be built to have different effects on the flyability, take off ease, landing ease, and basically anything else you'd want to know about your plane. In short, as long as you have your Center of Lift behind your Center of Mass, you should have a plane that at least won't be spinning around every few seconds.
1: Center of Lift Basics
The Center of Lift is basically where the wings are lifting the plane from. This is a consise explanation of how this affects flight. Click here for page 1.
2: Center of Thrust
The Center of Lift's relation to the Center of Mass is usually the most important, but that assumes that the engine is in line with the center of mass. This graphic shows how the Center of Thrust impacts performance. Click here for page 2.
3: Control Surfaces and Wing Shapes
Control surfaces are critical to controllable aircraft. Wing shape plays a major role in efficency. Click here for page 3.
4: Wing Alignment
The cross section of the wings (viewed from the nose of the plane) plays a major role in roll stability. See how wing shape effects aircraft stability. Click here for page 4.
5: Angle of Attack
The side of the wing that faces into the wind plays a major role in the ability of the wing to generate lift rather than just acting as a parachute. Some clever plane designs can even utilize this for specialized tasks. Click here for page 5.
6: Landing Gears
There are several landing gear configurations. Each has its advantages. This section does a great job of showing how landing gera configurations affect a craft. Click here for page 6.
7: Landing Gears Continued
The guide I'm pulling this from had enough content on landing gears to deserve 2 separate pages on the subject. Click here for page 7.
8: Credits
This final page just shows a very Kerbal example page and provides a short conclusion to the lesson. Click here for page 8.