How DO you get good graphics??

Once you've got your professional-looking sprite images and expert 3-D models, there are then further techniques used to create the effects, lighting, shadows, sprites/particles etc. that add s much more to the appearance of the game. For more specific stuff like this,

i.e. "How do I make fog?"

or

"How can I make blood splatter up the walls?"

etc. etc.,

Look here or ask generally on the forums!