It will be kinda obvious but look out for wear around the flipper buttons if it doesn't have the lollipop rails .

Check for a broken funnel at the entrance to The Ring ( easily replaced but a bonus if intact ) .

Check for a broken / damaged "Arwen" plastic . It's the plastic below the exit of the Path of the Dead mini playfield on the left . It normally has a picture of Liv Tyler's face on it . ( Again , easily replaced , and there are options for protectors to install to prevent further damage ) .

Apart from that check for playfield wear etc.

Great game . One of Sterns best , if not the best .

As above, also

Look for wear around the 2 scoops and the drop into Orthanc, cliffys are available for these
Check all LED's in the ring light board are working (3 elf, 7 dwarf, 9 men)
Check how smooth the Balrog runs back and forth and that its switches all work properly for opened and closed
Minor point but early (non-LE) models have lots of figures on, check they are there. Can get replacements on eBay

make sure the magnet works in the ring.

Check code to see if destroy the ring can be set to one ball. (under one of the menu options, new ROM allows this)

Check to see if the Belrog light has the LED fix or is still using the original incandescent bulb. I didn't realize he was supposed to light up for the first month I owned it.

Look for a 906 bulb behind the back of the playfield directed towards the back left of the ring. It's timed to flash as activated by the spinner. It's usually a dead bulb due to it's location.

I think mine is dead now that you mention it.

There's also a flasher behind the tower on the right. Flashes in the shape of an eye.

No acid damage on whitestar CPU

Make sure that the Orthanc diverter gate is not stuck. The manual is a bit confusing as to how to make adjustments.

check to make sure it can reach valinor. I have had my machine for over 2 years and have yet to see it. I am sure my machine is broken.

I really like this game, but it can suck if the palantir target causes airballs. Check for that.

https://pinside.com/pinball/forum/topic/lotr-ball-hitting-glass-off-the-palantir-target

It's also commonly pulled out or burnt out by the magnet, suggest replacing with an LED and use some hot glue to keep it in place.