Always use tools like expertflyer, ita matrix, and even the AA downloadable schedule (pdf) for checking city pairs for operating carrier.

Always have Admiral's club access as dealing with IRROPs is usually alot easier to handle with the on-site club then via the phone lines

If you are an AA elite (EXP,Plt,Gold) always try to buy on American Paper ('001 ticket) as during IRROPS as when IRROPS happen it is easier for the AA folks to pull and reissue the ticket then through the US Air .... same rule applies in reverse for US Air folks (make sure you buy US Paper ('03 ticket number)

Alcohol ... as you will need it as I have only been able to online check-in once during the December 2013 to current merger mess .... and needed something to clean out my internal filters so I don't scream at the gate agents

Online spreadsheet (google) with AA Locator, US Locator, Ticket Number, Flight numbers and city pairs. I have used this many times with the admirals staff so they could see the itineraries if complex to help find information

The only time I have bought US Paper for US flights as an AA EXP is when I know their is reward/upgrade availability for a flight, and I want to use miles for an upgrade; however, buyer beware as IRROPS can be a pain as getting a hold of the staff can be a PiTA.