Well, it's not that hard, actually. Take those doodles and a sheet of tracing paper and a light table (they can be pretty cheap - look at Michaels...or any other arts & crafts store, particularly those that cater to the scrapbooking crowd. get one that's a little bigger than your drawing paper) and some masking tape.
tape down the corners of your drawing, then tape the tracing paper over it. trace the major lines, see what the flow of action is heading towards in the doodle, find the major ovals, triangles, or other shapes. what lines make it look more like a 3d form, and which seem to flatten it out? are there any that are redundant?

play around with it like that and use as many layers of tracing paper as you like. then, take all those layers and refine them down to one final-ish image. how's the composition? it may help to draw a box/oval/other shape around the image, like a frame, to give you something definite to relate the image itself to - white space is as much a part of the image as is the line!

then, once you've got a final image on the tracing paper, trace that onto some good stock, something that will take inking or coloring or that will simply scan well.

that's what they teach us in Graphic Design, so hope it helps