Sth you really like to do -- to understand yourself is not easy, very often we don't know what we really want;
Sth you are really good at -- this will reduce your opportunity cost (note: this is more of a self-examination, rather than comparing to others);
Sth that makes money -- a good technology/skill without a good market doesn't really help.
其他的就不多說了,仁者見仁,智者見智。
歡迎建設性的交流看法。