Depends on the model, but the rule is to make sure your object 'pops' off the background, as yours does now. It varies. With that said, I would set your diffuse color even darker then it is now, you want to fairly dark to sell the surface details better.
My typical setup: Dark grey diffuse, 70-90 on the rgb scale. Strong spec, 60-90% Wide-ish gloss, 20-40% Then I use a 3 point light setup. Marmoset did a good tutorial for TB1 that applies to any 3D package: http://www.marmoset.co/toolbag/learn/character-lighting Make sure to have realistic quality viewport mode on (or…