Let me start by saying this as a proviso... I'm not a professional at this... a hobbiest. Though I 'd do myself a disservice if I didn't say something here. I have dicked around with maya since it was Alias and/or WaveFront Maya 4. Here is my two cents.

Learning to model with good edge flow in mind is most of the battle.
Seems like a simple thing to say. But, it saves a milion hours in later life. I can look at something and already know how the edge flow will work. Just take your time. I 'shadow model'. I fear I'm coining that phrase. I mean. Look at the object then make adjustments. If that makes sense?!

If you have good edge flow... then distoprtion on the UV's is my next thing.

Don't slap dash a projection map onto your model and call it a day.

I, as I'm modeling, already know how I'm gonna layout the UV's. Pre-planning is the best for it will save you a million headaches later. Evrey case is different so there is no hard and fast rule for UV'ing. There is Maya mel-script plugins... some good some terrible. It's just worth learning to UV for yourself. It will make your choices better.

Rendering...

I use Arnold renderer.

My process though.  I rough out the geometry in maya. The import an OBJ into mudbox and use my tablet to scult the deatails. then re-import the low res mesh back into maya with a normal/bump/Ambient Occlusion/Specular/ etc texture maps.

Rendering with Arnold...

I render in passes.

Spec map

Beauty pass

Amb Occ

etc.

Then I take then into Photoshop or After Effects to composit them.

I can go into more granularity about this lol. But, I'd rather not.

I mean mean file types for texture and the renderer is a weird thing of its own.