The method imparting photo to a pencil drawing using Photoshop is described in this tutorial. Try to use photos with degraded background and large objects in the foreground with legible contour for reaching maximum effect. You must degrade the background by filter Gaussian Blur, if your photos have legible background.
As an example I will use the photo of a sportsman. The drawing size - 508X764.
1. Make a copy of the layer with drawing by dragging it on the icon "Create a New Layer" on Layers. Press Ctrl+Shift+U for desaturating drawing on the upper layer. Apply Filter > Stylize > Glowing Edges with the meaning Edge Width - 1, Edge Brightness - 11, Smoothness - 5 in this layer. Regulate Levels [Ctrl+L] in such a way as to highlight the maximum of the significant lines of drawing.
2. Press Ctrl+I for inverting drawing on the current layer. Apply Filter > Artistic > Cut Out with the meanings No. of Levels - 7, Edge Simplicity - 3, Edge Fidelity - 3.(pic.4)
Regulate Levels [Ctrl+L]as in the pic.3.
3. Make a copy of the current layer by dragging it on the icon "Create a New Layer" on Layers. Apply Filter > Blur > Gaussian Blur with the meaning Radius - 5 pixels by new layer. In Layers set the blending mode 'Screen' for this layer and set Opacity - 50%. Press Ctrl+G for grouping it with the lower layer. Attention! Before pressing Ctrl+G activate the main drawing.
Well, we have an interesting pencil drawing.(pic.5)
4. Now, let's add colours to the photo. Switch over the second (pencil) layer and set The blending mode 'Overlay' for this layer. Switch over the Background layer and apply Filter > Noise > Median with the meaning Radius 5 pixels for imitating water-colour. And that's it. See how you created a pencil drawing from the photo using Adobe Photoshop 7.