Ok, I know I keep going on about it, but really if there's one aspect of a scene that can make or break the image more than any other, it's the lighting. You might have the most incredible landscape or stunning portrait model, but without the right quality of light and knowing how to make best use of it, you can still be left with a flat, dull, and uninspiring photo, so it's often very important to find the right time of day to shoot your outdoor scene.
This brings me neatly on to the The Golden Hour in photography (or sometimes 'Magic Hour'), it's roughly the first hour of light after sunrise, and the last hour of light before sunset. The exact times and durations vary depending on the time of year, and where in the world you are. The further you are from the equator, the longer your golden hour. During the golden hour, the sun is low in the sky, producing a soft, warm light which for most subjects is more flattering than the harsh midday sun that we're sometimes unable to avoid. The light at these times is also less contrasty, which reducing the chances of losing parts of your subject in strong shadows or blown-out highlights. The warm glow adds a pleasing feel to the scene, and the long shadows help to pick out details, adding texture and depth to the image.
And if that wasn't enough, there's an added bonus, there are generally fewer people around at dawn and dusk than there are at other times of the day, giving you a chance to capture your images in peace and quiet.