Deventer is on the main rail line between Amsterdam and the German border, with regular Intercity trains and very fast connections to the rest of the Randstad. From Amsterdam Centraal, the journey is around 1 hour 15 minutes, with one or two trains an hour. From Utrecht it is 45 minutes. From Schiphol airport there are direct trains roughly every half hour.
The station is on the western edge of the old town, a 5-10 minute walk from the Brink. By road, the A1 motorway (Amsterdam-Berlin) runs directly past the city. There is no airport in Deventer; the regional hub is Amsterdam Schiphol, although Münster-Osnabrück across the border in Germany is also reachable. The old town is compact enough that, once inside the walls, you will walk everywhere.