You can ask 10 different people and get 10 different answers. I can only offer up what I have found that works best for me.
I still have not been able to achieve hyper-realism. However I have found a few tips/tricks to help get me closer.
1st: Just as mentioned by Reggie, you don't want to use graphite for the darkest areas as they will create a shine or reflection in light. You want to use a charcoal based pencil. I have found the Primo Elite Grande works great and can be purchased at any Michael's craft store.
2nd: Paper is key. One of the keys in achieving a photo realistic image is having smooth paper. I use Bristol board, which is a thicker stock paper and has a smooth and textured side. I always use the smooth side.
3rd: Blending tools. The tools you use to blend will impact how smooth, rough, or textured your blending turn out. I have found that for real smooth blending I use q-tips. Other tools are soft tissue, cotton balls, chamois, and stumps and tortillions.