Depends on school and department.... A lot of schools take the test as "something you need to do for application". You just need to take it and it does not hurt you if you do poorly. If a school consider it, it will tell you that you need to have a "competitive GRE score". Read carefully when you apply.
Good GRE score will NOT guaranteed you a certificate of admission. You should show other stuff that will impress the committees. For engineering students, show them your EIT cert. (if you have one). It will tell them you have the basic knowledge as an engineer. Also, provide them your resume to show them what you have done after undergrad.
Good luck!
GRE: V: 320, Q 760
Applied:1.5 (1 school, 2 programs)
Accepted: 1
Rejected: 1