Foaming is the number one complaint with home draft systems. There are a lot of reasons why draft systems foam. The main ones are temperature, line size and pressure. The symptom you're describing sounds like it's not "laminating." This is the term for CO2 being in the beer and released slowly over time.
Temperature
The carbonation temperature helps determine how much gas is absorbed by the beer. There are lots of tables around to help you determine this for the right level. The colder a beer is, the more CO2 is wants to absorb. If you carbonate at a higher temperature, as the beer cools, it'll absorb more.
If there is a big swing in temperature within the line or into the glass, the beer will foam. Make sure your draft tower has cold air going into it. The shanks should be long enough that they conduct cold from the keg chamber.
Pressure
The first part of pressure is that pure CO2 dispense pressure needs to be the same as the carbonation temperature. This maintains equilibrium with the beer. Again, refer to the CO2 charts and make sure the beer is at the proper temperature for the pressure.
Constant release and repressurization of the beer causes loss of head retention and can promote oxidation staling. The proteins used in head retention only work once and even though there are lots of them, it takes its toll. Often, you'll see tiny white floaties in filtered beer, which form because of too much foaming. They also form in stale beer.
Line Length
This is where the first two items need to come together in creating the system. The dispense pressure needs to equal the resistance of the line plus height of the tap, minus one pound. So, to put it another way, the line length needs to be matched to the dispense pressure.
What's the resistance factor?
Resistance values will change based on what the line is made of. This is for the inside diameter of vinyl, the most common used in brewing:
3/16" (4.75mm): 3.0 PSI/ft. (67.9 kPa/m)
1/4" (6.35mm): 0.8 PSI/ft. (18.1 kPa/m)
5/16" (7.94mm): 0.4 PSI/ft. (9.0 kPa/m)
3/8" (9.53mm): 0.2 PSI/ft. (4.5 kPa/m)
The simple rule is the bigger the diameter, the less resistance. Simple, right?
Putting it Together
From a carbonation chart, we see that a beer kept at 40F (4C) will need just 12 PSI to maintain 2.5 volumes.
From the list above, we can see that 1/4" tubing has a resistance of 0.8 PSI
To get the right length of 1/4" ID tubing, we want to divide the dispense pressure, minus one pound, by the line length.
12 - 1 / 0.8 = 13.75 feet. That's a lot of tubing!
Looking at 3/16" ID tubing, we get:
12 - 1 / 3 = 3.6 feet. Much more reasonable length!
I've simplified this formula a little because I haven't included rise pressure or other hardware. The differences are small, so a rule of thumb is that about four feet of dispense hose and ~14 PSI is perfect for most applications.