In the image above there are 9 distinct types of noses. Obviously, you could devide noses into hundreds or even thouands of different categories. But, I usually use only the types you see here. These are noses that I know. This may seem to be kind of limiting but it does a couple of things. Firstly, noses don't lend much to expression but they are a good tool for defining character. By limiting my choices I can just grab one out of my little bag and stick it on my character. Secondly, limiting the number of choices I use for noses, eyes,ect. helps to establish an identifiable style that is mine. This is not to say that you shouldn't experiment. Be bold and creative with your cartooning.
Notice that there a no "feminine" noses pictured above. Most noses are uni-sex. But you should usually make a females nose petite. Also, notice that all the noses are side view. You can, and I almost always do, use side view noes for front view faces.
Drawing noses is one of the places where using a computer is especially handy. Most nose are quick and easy, requiring one or two actions to draw. Most of the time I'll draw the nose with one curve(using the curve tool). You can get quite a few noses this way. The nose we are going to draw here is just two lines. The noses at the bottom(in above diagram) are one oval. The rest of the noses you kind of have to draw one pixel at a time using the freehand tool.
What I will usually do is draw the nose off to the side a little.Then, when I get the nose I want I can just paste it onto the head. Before I paste it I color it green. I do this so when I paste it, it covers what can't be seen behind it.
Notice that the nose is where our guide lines intersect. You can of course put it higher or lower if you want. How high or low the face is can make a big different in defining character. I usualy, however, just stick the nose right where the lines meet.
The character that we are drawing is a mad scientist and is a little twisted. The pointy nose is going to help explain that he is sinister. It does not make him sinister. It only helps describe him as such. The eyes and nose will work togther(along with the rest of the facial features) to describe the character.