Expired Domain Due Diligence

Besides checking if it's deindexed, are there any other important things to check for? What should I keep an eye out for? Does N/A PR have any significance?

I would check it's backlinks and see if they are natural. You can tell by the keyword used, and by looking at the pages the links are coming from. I sometimes run over domains with spammy links, I'd def avoid these.