Go to aa.com, use your PNR to pull up your reservation, and request upgrades. Alternatively, you can call the phone number on the back of your gold card and request upgrades that way. If they don't clear by the time you get to the airport, request again when you get there. Do not offer a tip.

(Also, I'm not sure how the ability to enter your AA number into the reservation gets you 1/2 points.)