Don't WD-40 the shit out of everything.
You need a non-petroleum based lubricant for the rubber bushings.
Check the anti-roll bars, and their bushings to make sure nothing is worn or too loose. Then check the rest of the suspension bushings...if one of those is worn or cracked and you've got metal touching metal it'll squeak. If that still doesn't work then have the brakes checked...sometimes if there's a problem with the brakes or rotors it can make a squeak like that. If that's not it...well, then I'm stumped.