Many people struggle when it comes to drawing mouths. For this tutorial I will show you how to draw a realistic looking mouth. At first try, drawing lips seems very difficult. Your first drawing comes out simplistic, the next over-detailed and wrong. It seems that without a complex understanding of shading and depth, you'll never be able to draw a perfect pair of lips. Not true! While all art is subjective, this article will give you a basic understanding of how to draw lips in a realistic fashion. Use this as a jumping off point to let your creativity flow.
Step 1:I began with a basic outline sketch of the mouth. Identify where you want the lips, teeth, and gums to be.

Step 2: I laid down some graphite above the top lip. Tones will be darker towards the outsides of the mouth. Don't worry about precise shading at this point because this area will be blended later. Just scribble some tone down on the paper.

Step 3:Next, I used a blending stump to blend the graphite around. I used blended circulism for this step.

Step 4 :I moved on to the top lip. The bottom of the top lip will always be darker than the other parts so I used a 3B pencil and laid down some tone in this area.

Step 5:Still using a 3B but applying less pressure, I started laying some tone down on the left side of the upper lip.

Step 6: I began working on the gums. Remember that the gums have to be darker than the teeth so don't make them too light. I used a B graphite for them.

Step 7: Next, I started working on the teeth. I notice alot of beginners think that teeth are white. Teeth are not white. The only thing that may be white on teeth are the highlights. Teeth have brilliant highlights so pay attention to your reference picture and draw around these. If the highlights don't stand out like you want them to, darken the area around them. I used a 2H on all of the teeth.

Step 8: I finished up the teeth and moved onto the bottom lip. Bottom lips can be tricky because they usually have several different tones on them. I started by laying down some of the darker tones with a 3B.

Step 9: Here is the final drawing of the mouth. There is always a dark area just underneath the bottom lip. Also, the lips were blended in slightly to the surrounding skin. Tone adjustments can be made at this time and details can be added too.

Drawing a mouth is not hard to do. Just like any other type of drawing, it is mostly about observation. Because mouths can tell us a lot about the mood and expression in a work of art, it is important for us to be able to render them accurately. Although you should never use a standard formula when you draw anything
I hope this tutorial has helped you in some way or another. I can explain how I do things all day but the basic idea of drawing is to just understand how tones flow and to train your eye to see what others don't see.