it really depends on what your looking at, and make sure they aren't actually photos of objects.
details come in when you pay attention to the texture something has. glossiness, how it refracts, the shapes and contours. you have to practice and observe. you can use textures and just shade over them and make a rubbing if you need to. observe the item carefully and then practice - a lot.
---Mike Savad
MikeSavad.com