I try and draw in "realism" as much as possible, although im still learning this technique. I`m hopeless at drawing fur which is why my drawings have the more sleek look..lol.
A lot depends on the shading when trying to get parts like the noses and eyes to look realistic, you need to get the tones right as to where the light is hitting and where there are shadows etc. I also use many layers of graphite depending on how light or dark an area should be.
It can take anywhere from a few hours to many days for me to finish a drawing, a lot depends on the references I use and how clear they are to see, sometimes it takes a lot of guess work and imagination to get things right.
I do tend to mainly draw horses as they`re my passion, but its good to branch out occasionally and draw different subjects, it keeps the mind fresh..lol.
I recently drew this picture of "Edward" from the Twilight movie for my daughter.
I hope this has helped somewhat, i`m not very good at explaining things! :)