In iTunes, build a standard playlist with the songs you want, leaving the least wanted near the botton of the list.
Under the File menu is a option to burn playlist, choose the audio cd option, you can possible place about 10-15 songs on a audo cd (CD-R's are fine)
When iTunes says do you want to burn across more cd's say yes, then cancel after the first burn to fill up the first cd, unless you want to burn more cd's.
CD's are better than iPods in cars because if a burned cd is stolen, lost, scratched, damaged, loaned you can just burn another.
I've had two iPods stolen out of my vehicle, that's the last time I use iPods. Plus it's so stupid, playing the same songs again when I restart the car. Long trips it's ok, but not for short trips. I like the ability to play the exact songs I want, in the row I want, the 10-15 playlist selection of a audio cd is more ideal method in my opinion. Especially all the concern over inattentive driving.
If your car had a MP3 playback ability (MP3 is a compressed digtial file format which the stereo would decode) you would need to convert the AAC format of iTunes to MP3 format.
Good thing about MP3 format, is you can burn about 100-150 songs per cd.
Some car stereos perhaps can handle AAC along with MP3 decoding, but you would have to find out and install one, that way you don't loose quality due to having to convert formats.
Perhaps the best car stereo would be one that decodes AAC format and reads data DVD's, perhaps dual layer even, that would give about 9GB of songs or about 1800 songs per DVD, 900 per side. I've only seen something like this on home stereo systems.