Simple dusk silhouettes are fun to shoot and easy to mess up.
Two key tips for me: (1) overexpose slightly to get nice pastels in the sky rather than blood reds; and (2) find strong, separate shapes to frame against the sky.
On this image, the pastels are nice,and the silhouettes are good, though not great. The windmill, tree and tank are strong shapes and not overlapped, but the cows are sort of a mess (except for one). I remember waiting for as long as I could for the cows to separate, but they never really did. Still, a good but not perfect image is better than nothing at all.
Cattle and windmill at sunset, near Marathon, Texas, USA. Canon Ds. Mark II. 155mm. ISO 800. 1/5 sec. at f/5.6. EV +2/3.