If you're flying into Milan you'll mostly likely land at Malpensa Airport. If you are arriving on a domestic flight or the occasional European flight, you may also land at Linate. A third airport, Orio al Serio Airport is also used for low-cost airlines.
From Malpensa use the Express train into the city, taking about 40 minutes.
From Linate take bus 73 that connects to the metro at San Babila Station on the red line, one stop from the central Duomo Station.
From Orio al Serio take the shuttle bus into the city.
From and to any of these airports you also have the following options:
Private Arrival Transfer
Private Departure Transfer

If you are arriving by train from within Italy, you'll end your journey at the city's Central Station.
To get around the city, the best option is to use the metro which covers most of the attractions you'll want to see.

Milan is also a popular gateway to seeing the rest of Northern Italy, for which you may want to rent a car.