Milan is a year-round destination, but some months are better than others. May and September are best as the weather's likely to be good but it won't be too crowded. July and August are the Italian tourist high season, so the city is busy but buzzy; from mid-June to mid-August it tends to be hot and humid. October is the rainiest month, and from November to February it somehow manages to be cold but humid! Avoid the Fashion and Design Weeks (1 in Feb-March and 1 in Sept-Oct) as everything gets booked up and the city becomes very hectic.
Note: flight, boat, train and bus timetables change constantly, and airlines come and go, so please do not rely solely on this information for your travel planning. Check with relevant companies, or a flight search engine like Skyscanner, first.
Milan is served by 3 international airports - Linate, 8km to the east, Malpensa, 39km to the north-west, and Bergamo, 46km to the north-east. All have good shuttle connections to the city centre.
From the UK:
Alitalia flies to Malpensa and Linate from London Heathrow.
British Airways flies to Malpensa and Linate from London Heathrow, and to Malpensa from Manchester.
EasyJet flies to Linate from London Gatwick.
BMI flies to Linate from London Heathrow.
Ryanair flies from Bristol, London, Liverpool, Glasgow, Leeds and Nottingham to Bergamo.
From the Europe:
Brussels Airlines, Air Berlin and Norwegian all fly from a wide range of European cities to Malpensa, and Brussels Airlines also flies into Linate
Ryanair flies to Bergamo from a good range of European cities, including Italian ones.
Milan's public transport (ATM for central Milan, SITAM for greater Milan) is impressive: there's a clean and efficient metro system (6am to 12.30am), plus regular buses (5.30am to 1.45am), 24hr trolleybuses and trams (4am to 2.24am). It's also incredibly cheap - a single, multi-transport ticket is €1 to anywhere in the city, while a 1-day pass is around €3 and a 2-day pass around €5.
As part of a major ecological initiative, Milan now has an extensive bike-sharing scheme with long racks of yellow bicycles visible all over the city. You must register first, buying a temporary BikeMi subscription at one of many ATM information points (there are 2 in the metro station under the Duomo). They don't come with helmets, so take care on the often-congested streets.
Driving wise, it's strongly recommended that you leave your car at one of the huge commuter car parks just off the city's ringroad, which are all close to metro stations, and take the metro into town. There's a congestion charge of €2-10 per weekday for driving in the city (depending on the age and engine size of your car), a tricky one-way system which could confuse, and parking spaces can be hard to find, as well as expensive. If you want a car to explore the region then see our car rental recommendations.