Being a Starbucks aficionado and NRT freq. traveler, I always like to recommend the Starbucks adjacent to the Skyliner/ Narita Express/ local trains ticket barrier in Terminal 1 It is on the basement level). I do so because there is only on train station, the barriers are right next to each other and Starbucks sits immediately in front of both.

The are are other Starbucks at NRT but they are in the terminals so there i no way to go to the wrong SBUX.

Just follow sign for the train platform and when you see the ticket counters, slowly rotate yourself up to 360 degrees and you will see the Starbucks in front of these counters. Very very easy.

Mike