You need to check with your local gun laws. They vary state to state and you need to make sure you follow YOUR laws, what others can suggest and do in other parts of the country means nothing to you.
In many states, a simple face to face transaction is allowed.
However, in many states its not. Any state with any kind of waiting period its likely not. You'll need to go through an FFL or your state police in some states and they will help carry out the transaction and do the appropriate background checks etc.
You cannot sell to anyone out of state without going through an FFL in THEIR HOME state.