I just bought my 04 6 months ago...
Standard Stuff:
Check the oil, make sure it is mostly clear, most dealers will change it before you get it
How much tread on the tires?
CarFax, if not clean (no accidents, etc) drop the price, look at ebay autos also, check out the finished and sold auctions.
When does the warentee expire. With an 04, you may be able to get one with a few months remaining on the bumper to bumper.
Check all the electronics and automatic stuff.
Put the top up and down, couple times, it is very smooth.
Verify the GPS works, if it is a Lexus dealer, request an upgrade to the DVD
Verify the radio/cd changer/tape function, take six disks to insert and remove
Verify the woofers are not blown
check the seat controls and memories
Stering wheel adjustments and memory
Mirror adjustments and memory
check the trunk, hook, gas opener
check the climate control, both heat and ac
Verify the tires. Runflats/no runflats. If no runflats does it have a spare?
Look under the front, scratches
How's the paint, swirl marks or spider webs, nicks, dents
How do the wheels look, missing any lugs
Everything in the "emergency kit" (jack, allen wrench, drivers, etc)
Check the traction control and sport mode settings
Cup holders/ash trey open/close smoothly
Flaws in the wood and leather
Doors, trunk, hook all close w/o effort, this car is solid and when the doors close the sound is solid, just a light push and they close completely.
Drive.
Top down and radio off, rattles, squeaks, etc. There should be NONE, NADA. The car is very solid.
Owners manual
Remember this was a ~$6x,000 MSRP new car, just coming out of bumper to bumper, it should still be in top notch condition.
I did not even consider anything w/o a clean carfax. They may have been a better deal, and if you are handy with cars or know a mechanic that can work on these, well that may be a better choice for you.
If you have other questions...
sapp at pobox dot com
Hope this helps.
Kevin,