Getting a keg to pour optimally is an interesting battle. You need a number of things to be set up correctly to make it work. First, you need the right temperature. Second, you need that temp to be consistent all the way to the faucet. Third, you need the right serving pressure for the beer and temp. Finally, you need the right hose length for the serving pressure.
If any of those are too far off, you end up with either a foamy first beer or all beers are foamy. If you've looked at carbonation charts, you know that how much CO2 will be in solution is proportional to the temperature. Lower temp beer can hold more CO2. So you need to look at the chart to force carb and use the same info for serving pressure. Ganerally, serving at 37 degees or less is optimal from a pouring perspective (regardless of ideal drinking temp).
If the beer line is warmer in the tower, the beer in the line warms up and you get CO2 coming out of solution. That CO2 forms a pocket and results in a foamy first beer. One poured immediately after will not produce that foam. It's not flat, it's just not readily coming out of solution. You can pour that more aggressively if you want a nice head on it. I use a tower chiller that keeps the air recirculating through the tower and the rest of the chamber for consistent temps throughout.
The line length ensures that the beer doesn't come out too quickly for any given pressure. Flow through a hose or pipe is inversely proportional to the length and directly proportional to the diameter. A smaller diameter and longer hose will flow more slowly and reduce agitation as the beer enters the glass.
One final thing to consider. There was a person here who had a special lid for a corny keg for carbonating that fed the CO2 through a carbonation stone into the beer. Works nicely for carbonation, but you want to switch to the regular gas in port for serving. Once carbonated, introducing CO2 into the beer through that creates nucleation points and takes CO2 out of solution. This makes beers after the first one pour flat until a day or two later when the beer is re-force carbed. (at least that was our conclusion at the time and moving the gas input solved his issue).