I love sunsets. And silhouettes. And reflections. When an opportunity comes along to combine all three in a picture, I just can't resist.
To get a nice silhouette it's often necessary to under-expose the image by 1 - 2 stops. As luck would have it, this also has the side-effect of saturating colours more, which can really emphasise the sky colour in a sunset. You can also set the white balance of the camera to cloudy, or even shade, to super-saturate oranges and reds. This is a matter of taste / personal preference. If you shoot raw images, rather than jpegs, it's very easy to undo the effects of these setting later by resetting the colour temperature in your raw editing software (e.g. Lightroom, Aperture, Capture One etc.) Silhouettes need to be really sharp - there's no detail in the black shape of the subject, so the eye is drawn to its outline (that's just the way our brains work) and any softness there will be noticed. It's best to keep the shutter speed reasonably high to avoid motion blur, and use a sturdy tripod.
The closer you are to water level, the better the reflections will be. For a perfect reflection in water you'll need an absolutely calm day, and a motionless subject (if you look carefully at the reflection above, you'll see that there was a tiny amount of motion in the water - perhaps I'll have better luck with the weather conditions next time).