Newbie: rendering

How do you increase the rendering sharpness in Blender?

When I render a simple scene, such as a cube with text using the default Blender fonts on one of its faces, the items look flat and jagged in the final render. What should I do to make the final render better quality?

Put a motion blur, maybe?

Or smooth the text, maybe?

Or making world black, not default blue? (maybe)

or set the osa to 8 or 11

For the jagginess:

What do you mean by “flat”?