I always have a Polarizer, 81B Warm Up, and Neutral Density Graduated filters when I got out on a shoot. This allows the colours to be more intensified and helps with contrasting situations.

1. Polarizer – Great for those skies with putty white clouds. Stand the camera at 90 degrees to the sun and by adjusting the filter the sky and clouds will become more saturated. It also works well with reflections.
2. Warm Up – literally warms the picture.
3. Neutral Density Grads – Allows the photographer to get balanced pictures in contrasting conditions.