If you are looking for some help on your flight regarding your reservation or seat changes, then the gate agent working your flight has all of the tools to help you out. Airline gate agents have access to lots of information that the general public cannot see and can be your best friend when you need some help. In order to get the full attention of the gate agent it is important to know when to approach the desk. Heading up at the wrong time could get you a rushed and unfavorable answer.
Gate agents will typically arrive at the gate about an hour prior to the flight's scheduled departure time. It is important to know that the agent has many responsibilities while working a flight, answering customer questions is just one of the many things that they do. The last thing that a gate agent likes to see is a big line at the counter right when they arrive, so they will likely try to dispatch the line quickly to get to work on the flight.
If you have a question about your flight or a seat then you should wait for the gate agent to get fully set up at their computer. The passengers standing at the desk in line are going to get quick answers, but they probably won't get the attention that they desire. Once the agent has gotten settled in and made a few announcements they will be ready to take questions. Before you approach the desk, make sure you pay attention to any announcements that have been made about your flight, your issue may have already been addressed.
If you still need help or have questions, make sure the gate agent has settled in at their post before approaching. It's always better if there is no line so the agent will not feel pressured to make quick decisions. Be clear with your requests and the agent will be willing to assist you if they can.
You would be surprised to see some of the good seats that may become available after things in the boarding area calm down a little bit. Many people have experienced rushed or abrasive customer service answers, you can avoid these by giving the agent a little space and talking with them when there are less people around. You will almost always get better service after things have quieted down.