By FCC regulation, stations must identify at 10 minute intervals and at the end of the communication. It is considered good practice to identify at the start of each communication as well, as without identifying at the beginning, other stations will not know who you are, or they may assume your unidentified transmission was accidental or was made by unlicensed operator.
During the course of a conversation, there is no need to identify each time you make a transmission, only once every ten minutes. The repeater identifies itself at least once every ten minutes, so the repeater ID can be used as a rough guide for timing your station identification. However, if there are multiple stations in conversation, be mindful of how long it will be before you have an opportunity to identify again. While identifying excessively is poor practice and can quickly become irritating to those listening, it is better to be safe than sorry with regard to ensuring that you identify at least once every ten minutes. In the interest of expediency, avoid using phonetics when identifying at ten-minute intervals unless there has been a misinterpretation of your callsign by another station that warrants correction.
When stating the callsign of one or more other stations in addition to giving your own callsign, such as when making a directed call or during the course of a conversation, your callsign is always said last. "N0MRB, W8DLB" means that W8DLB is calling N0MRB, not the other way around.
Despite there being no legal requirement to identify the other station(s) that you are conversing with, common courtesy dictates that you should acknowledge and remember the name and callsign of the stations you talk to. Forgetting the name or callsign of the person you are speaking to is just as impolite on the radio as it is in person. It is extremely disrespectful to make flippant comments like "NRQ3X5 or whatever your call is" if you fail to remember it. Instead, you should respectfully apologize for forgetting the station's name or callsign, and after they remind you, be sure to remember and repeat it the next time you make a transmission. Consider keeping a station log or making notes to keep track of names and callsigns if you find it difficult to remember them. Recalling names and callsigns becomes second-nature with time and practice, especially when a concerted effort is made to remember them.
When ending a conversation with someone you have just met or who you do not regularly speak to, it is respectfully to say the other station's name and callsign, and thank them for the conversation, in the course of clearing your station such as "enjoyed the discussion Joe, hope to talk to you again. N0MRB, this is W8DLB, now clear".
If you have any suspicions as to the legitimacy of another station, do not converse with them. Check the FCC database or QRZ.com to confirm that they are who they say they are, and that they are properly licensed, to the best extent you can. Communicating with an unlicensed station is a violation unto itself.
