My 2007 prius squeaks the first 10 minutes of driving.

You need to lubricate the bottom of the car. Not sure where you live as you didn't fill out your profile so not sure if your seeing any winter. Fill your profile out.

I have been spraying grease on the bottom of all my cars for years. Not crazy but a little bit on every joint, nut, thread, bushing, bearing. Hood latch, hood hinges, door hinges, brake pivot point, etc. Then under the hood do the same. Spray a little on every electrical connector. It keeps moisture out.

Then use rubber revitialize spray on all the cvt rubber boots and the rubber boots between the doors for wire protectors. And all the outside trim. This stuff works good.

Every six months.
My underbody looks brand new on all my cars. And I have no squeeks.

This for metal avail at HD only:
http://www.levineautoparts.com/bl1.html
The great thing about CSP spray is it does not smell like WD40 or god help us PB Blaster.
That crap is awful. This stuff is a great product. Which means they should be pulling it off the market any day now.


This for rubber:
Black Magic Car Care Products - Black Magic Pro-Shine Protectant

 

Before you go spelunking with grease you should get a better idea of what is causing it. When is it squeaking? I would suspect it's coming from the brakes when they're still cold. Completely normal especially this time of year.