Here’s the main number for the FOX switchboard: 310-369-1000

If you call during business hours, ask the operator for Kevin Reilly’s voicemail. If the operator asks why you’re calling, say you’re calling about Lie to Me.

If you call after business hours, you can still leave a message:

When prompted, press 1# to access the dial-by-name feature.
Spell R E I L L Y on your keypad
Press 2 for Kevin Reilly
Leave a brief, polite message for him.

In all of your correspondence with FOX and Mr. Reilly please keep these tips in mind:

• DO tell him your demographic information (age, gender, and where you live, especially if it’s a major US city) so he sees Lie to Me’s broad fanbase.
• DO let him know if you are not a Nielsen viewer.
• DO be polite and respectful.
• DO keep letters/calls/emails brief and to the point.
• DON’T diss any FOX shows, or use this as an opportunity to complain about shows that were canceled by FOX (FYI, Kevin Reilly joined FOX mid-2007). Stick to Lie to Me.
• DON’T complain about a storyline, a character, etc that you don’t like.
• DON’T bring up things that are negative (like the Nielsen ratings). Not only is everyone aware, but we don’t want to hurt LTM’s chances. Stay positive!

Thanks to @Diotima12 for this info found at SaveLietoMe