GMAT Verbal & Essays

Guys,
I have my GMAT tomorrow morning, but still got some last minute doubts. If you can give me any info on any of the points below, it will be great. Weblinks will do too.

- Difference between "Compared to" Vs "instead of" Vs "as opposed to"

- Use of "who", "that", "those" should it be close to the subject it refers to or can it be far as long as the meaning is unambigous

- Use of "enough" (which of these choices is preferred - "hard enough to X" Vs "so hard that X")

- "instead of" Vs "rather than" (rather expresses preference of one over another?)

- Difference between "result of" Vs "because of"

- Use of "Comma" Vs "Semicolon" Vs "Colon"

Thank you,