This post is in response to a professor saying that it is hard to get students to make nice (publishable) renders. It isn't! There's a few bits of theory you should know (colour theory, basic lighting setup, rule of thirds, global illumination) but you can mostly fake it by borrowing other people's work, such as this this template for getting nice blender renders...
So getting a nice render out of blender takes a little tweaking. Here's a ready rolled blender scene and demo video for getting nice matte-white light-box renders with global illumination. Grab this template file here, and follow the video, or the following instructions.
First grab: blender, yafray and the gimp.
In linux, something like this:
sudo apt-get install blender yafray gimp
In windows, go to the websites and install (haven't checked that this works for yafray yet...)
Then start up blender. Load the template file. Delete the house-like thing you can see by right clicking on it, and pressing the delete key, and answering ok to the pop up box. Import the object you want to render. Obj is an easy format to work with when there's no textures. File->import->Wavefront(obj). There's a tutorial on moving stuff with blender here, otherwise select the object you want to move and use 'control-shift-g' to bring up the control widget, then left click and drag to move it around. "control-shift-r" (who makes up keystrokes like that?) for the rotate widget, and "control-shift-s" for scaling. The viewpoint when editing (not the camera) can be moved using a combination of control, shift and alt together with the middle mouse button (or tutorial here). To view the scene from the camera's pov, use the '0' key on the keypad (or view -> cameras -> camera).
This is the beast-of-a-render-panel:
After setting the aliasing quality (1), and the percentage render size (2), you can choose the frame ratio (3), before rendering (4). The combo box directly below the render button ("Blender internal" selects the renderer - in the example file it's set to yafray). At this point blender looks like it's crashed (if you're using yafray). After it's rendered (can take a while - go get a strong cup of something) push F3 with the output window selected to save in the format dictated by combo box (5).
You probably want to do a low quality render to check the details, before doing a full one (waiting 20 minutes just to find out that the top of the model is clipped is kinda annoying).
Once you've got the render, you probably want to open it in the gimp, and use colors -> adjust levels to get the exposure right for your medium (print, web etc...). Then save out the final image.