If you're an xONEx veteran, you already know this; however, if you're relatively new to this world remember to keep checking the itineraries for changes. I start a 16 segment DONE4 ex-CAI next week and was just reviewing it flight by flight. It was booked with AA; and I printed the entire itinerary from the AA system. I have found a few minor flight schedule changes. While in my case they turn out to be inconsequential, they may not be for you. I always do a detailed review about ten days out, then a final one a day or two before departure of the first flight.

An example? I had booked AA 1039 BOS-LAX departing at 1825 on July 13th. It's now been changed to AA 305 (instead of 1039) departing at 1802 (instead of 1825). I ended up finding five or six changes of similar ilk, flight number and small time changes. Then I go through the itinerary and check the seat assignments in case of equipment changes.

As I said, small and inconsequential changes in my case, but you should always check.

Edited to add: It turns out that a number of the seats I had selected have been unassigned, so I have to go through and select seats for those flights again.