NEVER EVER EVER have everything pale and then have really dark highlights!
Colour-code, don't mix and match the wrong colours together.
Don't pick dark lipstick then put really un-matched eyeshadow and blush.
Make sure your accessories are kind of alike in colour or shape to your makeup.
Dont over-do the makeup or accessories or vise-versa.
Never make your make-up messy. It looks un-neat and sloppy.
And the final golden rule: I see soooo many people copying other people's original looks. Makeup your own look and maybe you can start your own makeup fashion trend!