First impressions almost always are either a quick failure or success from a potential horse buyer looking at your horse photos. So, having great photos is essential. Interest from the buying party is made quickly. So make that first impression of your horse as appealing as possible.
Fill the frame with your Horse. Your horse should be taking up at least 70% of the photo. Photos can be fine tuned with a little cropping if need be. Use a telephoto lens or you might have to simply walk closer to fill the frame with your horse.
Make sure your horse is well groomed, this can make the difference with one brushing. You don't have to have the horse show ring ready. Just make sure you take the time to brush out the horses's mane, tail and forelock. Also make sure the horse doesn't have mud or tangles. Also, if you are using a rider make sure they are dressed appropriatly as not to take attention away from the horse (you are not selling the cowboy or cowgirl). Also don't use your everyday horse riding gear or halter make sure it looks crisp and clean.
Use the light to your advantage. Keep the sun to your back. Do not take the photo with the sun behind the horse. Pick a day that is not very dark and overcast. The best time to take photos is the horse is when the light is the most flattering, which is 2 to 3 hours befour sunset. The sun is at a lower angle unlike midday light that will make the horse's top line, neck and shoulders look bad by casting ugly shadows on the neck.
Horses look the best shot with long focal lengths. Wide angle lenses distort the horse, making whatever is in the middle of the frame look larger and everything else look smaller. This is why you shouldn't take a photo of your horse from the front angle. Most point and shoot cameras with produce this type of photo, so I would avoid shooting the horse from this angle. If your camera has good automatic setting use them if not set your shutter speed to 1/1000th and ISO to 400. This will eliminate camera shake and motion blur problems.
Make sure the spot you shoot your horse is flat and uncluttered, we don't want anything distracting the buyer from the horse. Always shoot from the horse's level. Be patient, great horse photos will help you make the first impression you are looking for.