There is no train connection with the airport.
Car and bus
The airport is 32 kilometers west of the center of Toronto and is easily accessible by highway 409 that connects to highway 401, the airport is also accessible by highway 427. The exits to the airport are easily indicated. You can see for yourself which terminal your airline uses on the signs along the highway.
There are several bus lines between the airport and Toronto. Line 192 from the Toronto Transit Commission (tel: +1(0)416 393 4636) is a shuttle connection (Airport Rocket) to the metro station Kipling (Bloor-Danforth metro line). TTC-bus line 58A goes to the station Lawrence West (metro line Spadina). GO Transit maintains express buses to stations York Mills and Yorkdale.
There is a special hotel shuttle bus (Pacific Western Airport Express), and at night there are buses between the airport and several destinations in Toronto (i.e. Danforth Avenue, Bloor Street, Yonge Street and Eglinton Avenue).
Car rental - Toronto Pearson International Airport
Car rental companies: Avis, Budget, Dollar/Thrifty, Hertz and National/Alamo have counters in the Arrivals Hall, outside the airport there are two more: Discount and Enterprise. You have to reserve the free shuttle bus in advance for these companies. You can also reserve a rental car in advance using the service EasyTerra provides, they compare the rates of several providers in a single quote.
Taxis are in front of all terminals and must adhere to the official rates. You can find the rates on the airport website, for destinations in Toronto.
There are parking garages by all terminals that directly connect to the airport. The rates for parking in the garages are $3.00 per half hour, with a maximum of $24.00 for the first day and $120.00 for the whole week.
Just outside the airport is a large parking area, Reduced Rate Lot, the rates are $2.50 per half hour, the maximum per day is $14.50 and per week is $65.00. The LINK-train goes between this parking area and the terminals.