Just some added thoughts:

 

1. Assymetry - Nothing in the macro-world is symmetrical. Everything is slightly off... (Sometimes, in more ways than one!) Never have a perfectly symmetrical ANYTHING in a render, unless your intent is to render some sort of Platonic object that doesn't exist in the real world. Always shoot for assymetry, ever so slight.

2. For human models, GOOD LOOKING HAIR! Try hard to get the hair as realistic as possible. No amount of awesome texture work on a figure is going to help be convincing if the figure looks like it's wearing a helmet made out of plastic hair. Here, you need excellent transmaps and very good materials to produce realistic transmapped mesh hair. And, if you can stomach Poser's hair room, you can try your hand at making any one of a thousand versions of long straight hair, short straight hair or spiky alien-looking afros. Good luck with getting materials to make any of those look realistic...

3. Lighting - Use only spotlights for anything other than an outer-space shot. Infinite lights are terrible for realism, but they can add good atmosphere, so you have to balance your needs. Use a point light with diffuse set to black and specular on to help pick up specular highlights without washing out the texture map. (Picked that up from a recent thread I read. BB, I think.) Do not overdue the specular, since we're not made of plastic!

4. If you suck at lighting, then the less you use of it, the better your renders will be! :D In other words, don't render out brightly lit conference room scenes with one shadow left by fifty differently oriented lights that wash everything out so it ends up looking like a bad comic strip. The best lighting gets around having to track fifty different shadows and subtle reflected colors. (In the real world, you can't have light without shadows...) Instead of a bajillion lights, use an IBL and maybe one spotlight, oriented appropriately with the IBL and maybe, just maybe, a point light or another spot in there, somewhere, to take care of what's needed without trying to duplicate, by hand, real-world lighting with a bajillion ill-suited fake lighting tools. (I'd give advice with 2012 pro and all its cool nifty rendering stuffs..  But, I'm still learning how to manipulate it.)

5. Staring at Vicky, naked in a temple, holding a sword, for years on end is going to do quite a bit to suspend your disbelief. I'll say this about V4 - I don't care who they think sat for the modeling of that figure and the rest of the figures in DAZ's or Smith Micro's stables. I don't care how realistic they say the accuracy was. In every case, none of those figures look like a real human being. None of them. The proportions are wrong, there are details that are missing that are impossible to model into V4's geometry, five hundred renders of women with the same exact bust size is certainly unrealistic and I've never met any guy that had the ginormous thighs these modelers seem to be in love with. Their "mighty thews" throw any semblence of realism out the window, along with Vicky's DDD bustline and neanderthalian vissage....

Get thee to a modelling program!

In other words, go grab a free modeller, buy Hexagon, buy ZBrush or splurge on 3ds and fix those models some realistic morphs so they look... realistic. Get yourself GIMP or Photoshop and do some custom work on bump and displacement maps. The key here is to start off with a good base from which to create a new and believable character that doesn't look like some Frankenstein of mismatched, ill proportioned morphs. Sure, these premium figures are wonderful! But, realistic? No. Can they be made to look more realistic? Sure! Can you achieve ultimate realism with them, right out of the box, even with standard morph packages? Not really. Instead, you have to put in some sweat-equity.

6. Don't forget Depth of Field! We are not Superman and we aren't The Who - We can't see for miles and miles, without losing any perception. Our focus extends to a very, very narrow part of our vision and, at that, only within a certain range of depths. Use Depth of Field wisely and realistically in order to help produce the best, most realistic, renders.

7. Here's where I talk about materials... There, that was easy - I'm done talking about materials. I can talk about geometry all day, but I know jack-all about upper-level material management and uber-hyper accurate material fixin's. I'll leave that to you guys and marvel at your magic!