Soon will be making first trip to Beijing. Are there Cirrus or Plus affiliated ATM's at the airport arrivals area?
If I get cash from an ATM machine, how/where at the airport can I change back any unused cash on departure?

I was there last month, not sure whether CP ATM is available. Bring enough Chinese $ for your land transport/local food/land tour packages/entry to attractions.
VISA/MasterCard/AmEx ATM available in airport and banks. These Cards are commonly acceptable at hotels, Restaurants and Emporiums. Beijing is great, interesting and reasonably cheap. BUT be aware of pickpockets, and be firm to reject Touts that are around to mislead you to take their service like tours/taxi/shop etc. Taxi waiting infront of hotels are there to cheat you. Walk another 150 steps away and take taxi that are plying on the road, they are bound by law to go by metering and issue receipt on the fee charged. They deserve small tips. At airport on the way to the designated taxi area outside the terminal, touts will intercept you to take theirs and bring you for a costly drive. Do not be led to so-call physician/medical hall. They use psychology to force you to pay US$100 for a bottle of honey syrup. Have a nice trip in Beijing!

Singapore: Thanks for your reply. I can always exchange a few dollars at the airport if I can't find an ATM. I've also read that tips in US dollars are readily accepted.

You may also want to bring some travelers checks. They are readily converted into yuan at most hotel desks. They have a better conversion rate than cash too. You can bring cash to convert, but make sure they don't look too "old" or even "new". They are very wary of counterfeiting in China.

If you convert back at the airport, make sure you save your receipts from the ATMs or hotels. They will ask for them. I didn't have any to convert back so I couldn't tell you where the desk is... sorry!

There are machines in the baggage claim area of the airport that accept $20 bills and deliver Yuan and a receipt at a decent exchange rate.

By and large tipping, whether in US$ or yuan, is practiced only by foreigners who don't know any better, or choose to ignore local custom.

In my Beijing Tour packet, Pacific Delight Tours has "tipping recommendations" & suggests small tips like 25cents per bag for porters.
But I will try to observe the "local custom".