I'm not really sure I'd consider myself someone who renders, especially not lately, but I guess the most important thing is learning the shapes and planes of things so you know how to shade it to suggest the volume. It's quite daunting but even a little goes a long way.
I usually keep my colours pretty simple, picking a midtone and then a dark tone, often a funky colour to scatter about, sometimes a highlight for butt shine etc. The way I currently shade isn't particularly blendy, more like a mushy cell shade, I generally just lay down my midtones, then paint the others on top. I use a brush that has a little bit of texture so the colours show through eachother. Anyway, do it scared etc. Ya gotta fuck up to make progress.