I always send an e-mail to the 1K desk (but other forms of communication work just as well) when I get excellent service. If I don't get the FA's name, I'll mention my seat number and a description of the FA (gender, sometimes race or hair length, what they were wearing--pants or skirt) to help UA figure out who should get the credit and I always get a nice reply with UA saying that they know to whom I am referring and noting that this will be placed in the employee's records and that the employee will be notified of the compliment. When I get excellent service from a CSR, I make sure to get his/her name and I contact UA as well.