How does a Congressman do it?

Congressmen are elected to represent their constituents and voice their problems, but how are they able to listen to each of their constituents problems while still effectively representing them from a completely different state? As Field representative for Congressman Doug Collins, Bill Kokaly said, "The most important job a Congressman has, is representing the people he serves." What tools do Congressmen use to connect with their constituents? How does a Congressional office work, and how does that aid in building a relationship between a Representative and his district?