methods to get renders to be as realistic as possible?

Marshian

I just did several tests using an interior set that has very large windows and good textures including glass, metal, wood, etc.. I experimented with spectral rendering, the architectural setting, various bloom settings, vignette, and caustics. I tried different combinations, switching them on and off. All of these were rendered with the default HDRI, the blurry ruins. None of these even closely compared to the realism that came from using a high-quality HDRI and a little DOF. I also added a very slight bloom: .005, 5000, 2.0.

I've added quite a few props to this set but one thing that really pushed the realism was using lights that have an IES profile (the three lights above the signage). These are from our set https://www.daz3d.com/architectural-lighting-rig-for-iray

I found the posts here very informative, hope mine helps too.

Quixotry

Also add asymmetry to faces, expressions, and poses when working with a character in a scene. Real humans aren't symmetrical, so just a touch of asymmetry on a 3D character can go a long way towards eliminating some of the "too perfect" vibe they tend to give off. No one smiles with the corners of their mouths turning up exactly the same way, and one eye may squint a little bit more than the other when smiling, etc. That and, as everyone said, good lighting, can make a huge difference in a render.

nicstt

Depends what exactly you're aiming for.

A render, basically an image, is a medium we use to tell stories.

First off: what story do you want to tell?

What style are you aiming for?

Are you going for photo-real? Is that everywhere?

If you want it to look real, then you need more than convincing lighting and texturing. For me, the composition of such things as pose, shape/morphs of the character, the way the clothes look and how they hug the figure all matter.

In the image you post, I get a stylised feel from it; the buttucks, breasts, hair and brows in particular are what give me that vibe. If that is the intention, then great - otherwise?

Photo-real needs help to work well. :) It needs help from aspects other than the rendering process. My opinion.

nonesuch00

The materials look real from that camera distance except the hair. The lighting looks like floodlights because with that much voluptuousness the artist couldn't bear one square inch of her to go unnoticed. The clothing looks like it was designed the same idea in mind. And finally the guns look like the character is thinking, "I'm tired of you Brad, get lost!"