Setting locales

I'm having a problem with my locale setting.

Essentially, when using Xmgrace or Awk, all . are replaced with ,
leading to wrong arithmetic.

Here is an explanation of the problem:
awk printing thousands with commas. see LC_ALL=en_US.UTF-8

How can I permanently set the locale to

LANG=en_US
?????

# in your .profile or .bashrc
export LANG=something

where "something" is one of:

locale -a

The reason I used "something" is because different unixes may show slightly different locale names. Plus locales are installed by the admin, so I may only have a few, whereas you may have dozens.