Most distro's have a group named "wheel" and you just need to make the user a member of the wheel group. Then look for the line near the end of the sudoers file with "%wheel". On a new installation you may need to uncomment the line.
Change the line like:
Code:
# Uncomment to allow people in group wheel to run all commands
# %wheel ALL=(ALL) ALL
and remove the "# " to uncomment the line:
Code:
# Uncomment to allow people in group wheel to run all commands
%wheel ALL=(ALL) ALL