The Fairlady Z emblem (ordered from thezstore) came with a template. All you have to do is unpeel the back, align the corners of the template and then stick away.
Quick note on debadging: Never try to pry them off with your fingers!! I tried prying off the Z part of the 370Z emblem from the top right side and ended up getting an indentation on my paint from the bottom left side of the 'Z'.
To debadge, all you have to do is:
1 Heat up the area with a hair dryer or a heat gun.
2 Use a fishing line or dental floss to remove the '3' '7' '0' and the 'Z'
3 Heat up the area again and the left over 3m from the emblem should rub off
4 There will be areas where it will not rub off so use Goo Gone with a microfiber to clean it off (use olive oil if you don't have Goo Gone).