Details on your setup would be good. Start with line size, length and temperature. Then what kind of faucet (picnic, tower with metal faucet, coffin, keezer collar, etc).
If you want to serve at 12psi you should around ~40ºF with ~12' of 3/16" ID beer line. That needs to stay cold from coupler to faucet. If it warms it will foam.
As stated, anything warm which would most likely be your faucet will cause foam. Knowing your system like was stated would help.
Is it just the first pint? if you pull a second pint is that one all foam also?