申請美國簽證 (好驚之下成功佐!!)

Just relax. You will be able to present yourself better.

You may read this article in Wikipedia:
http://en.wikipedia.org/wiki/Visa_Waiver_Program

It appears that the nonimmigrant visa refusal rate in US Consulate General (HK) is somewhere between 3% to 10%. In other words, most applicants would get approved.

if you are well prepared, not lying, and have no criminal record, it would be unnecessary to be nervous.