How do I improve a video's quality through Premiere Elements 8.0?

By that, I mean make the entire video look sharper. On my camcorder, the video looks alright, but when I upload it into Elements, it becomes blurry. I tried adding a Sharpen video effect, and when I rendered the video, I changed the size to 640x480 (from 320x240), increased its quality, and had the MPEG-4 setting.

While this did improve the quality a little, some parts are still very blurry. Any suggestions on how to further improve the video quality? Thanks.