Here’s a quick tip:
When you use levels to balance the colours/tones within Photoshop, instead of trusting the visible pits and peaks along the histogram, hold down the ‘alt’ key on your keyboard whilst dragging the black point and white point.
Now you will be able to see where the pixels are within your image in correspondence with the tonal range.
TIP: Drag in your black and white point markers to the point where pixels start to appear (whilst holding down the ‘alt’ key). If the pixels start to form ‘clumps’ then you are dragging too far. Try to achieve a ‘speckled’ effect, minus the clumps.