Analyze distance to vegetation on your render and real necessity for detailed materials - this way you shorten rendering time.
I always try to tell a story. Could be some elements or a light hitting one spot in the scene.
The main components of a great render are: interesting design, good composition, balanced lighting, realistic materials and right camera angle.
Remember: although optimizing textures size, lights and "general rendering setting" speeds the work, overdoing it, can ruin the end result.
To set lighting in a scene, you need to know some photography basics to understand camera settings and white balance.
Be self-critical with your work: try to find the balance between the time spent on a project and the quality.
I prefer to spend less time in 3d-software and more in postproduction. For me Photoshop is the best render engine.
Start with a small scene and shoot it like a photographer, remember the composition - it considerably changes the image perception.
Photoimages serve as the basement for fixing materials and lights. Results in 3d strongly depend on the choice of references.
Light is the most important in CG, above modeling and texturing; it gives the render right emotions, even without textures.
You need to spend time analyzing the real world to be able to imitate it. Inspiration comes from the outside.
To obtain photorealism, remember: everything in this world has a certain imperfection: color, reflection, geometry, placement or all of them.