Canada is large - the second largest country in the world after Russia. This means that you will need several days to appreciate even a part of the country. In fact, St. John's, Newfoundland, is geographically closer to London, UK, than it is to Vancouver.
By Rv
If you are set on a road trip, an alternative to car rental is to hire an RV motorhome or campervan. This gives you the flexibility to explore Canada at your own pace and is ideal if your trip is geared around an appreciation of Canada's natural environment. Costs can also be lower than combining car rental with hotels.
By road
Canada is a great place for hitchhiking, and is still quite common among younger travellers strapped for cash, or seeking adventure. It's most common in the far western provinces, where there are generally more travellers. Hitch hiking in the urban areas of Southern Ontario, and Montreal is not a sure thing as many drivers will not pick up hitch hikers in these regions.
As anywhere in the world, use your common sense when taking a ride.
By train
Passenger rail service in Canada, although very safe and comfortable, is often an expensive and inconvenient alternative to other types of transport. The corridor between Windsor and Quebec City is a bit of an exception to this generalization. Also, if natural beauty is your thing, the approximately three-day train ride between Toronto and Vancouver passes through the splendour of the Canadian prairies and the Rocky Mountains, with domed observation cars to allow passengers to take in the magnificent views.
Make arrangements ahead of time to get lower fares. VIA Rail (http://www.viarail.ca/) is the main Canadian passenger rail company. See also: Rail travel in Canada
By car
Of course, many people choose to rent a car. Although somewhat expensive if you are travelling alone, this can be an economically reasonable alternative if you are sharing the costs with others. However, there are many limitations and drawbacks on car rentals in Canada. To name a few of them:
there can be very high surcharges associated with dropping off the car at a different location than where it was picked up.
Unlimited km are usually offered for the province you rent it in only. As soon as you enter another province, even for a few km, your entire trip gets limited mostly to 200 km a day.
Driving is usually permitted on paved roads only.
There are no manual transmission rental cars available in Canada. Don't bother searching.
Basically said, if you really want to get around in Canada, except in Vancouver, Toronto, and Montreal, or places where there are few or no roads, it is best to have or buy your own car.
In some cases, frugal travellers may be able to "earn" budget automobile travel by delivering a car across Canada. The option is not common. Nor does it offer the opportunity to spent much time stopping along the way. However, it can be a cheap way to cross Canada while seeing the interior. CanadaDriveAway and HitTheRoad.ca are two options.
In Montreal, Toronto and Vancouver, public transit is a strongly recommended alternative to driving.
Gas prices are May 2011 in the range of $1.30-1.40 per litre in most urbanized areas in the country, but that is typical and usually goes up in March, just in time for summer driving season. Year round, prices tend to be about 50% higher than those in the U.S. after converting litres into gallons and factoring in higher taxes and the currency exchange rate. American drivers will generally find that their credit and debit cards do not work in gas pumps in Canada due to US cards generally not having "chip and PIN" functionality, although many of the larger chains such as Petro-Canada and Esso can run US cards via magnetic stripe if you bring the card inside to the cashier.
Of particular note is highway 407/ETR Express Toll Route in Ontario, which circles around the northern flank of Toronto. The 407 is an electronic toll road the only privately owned road in Canada, in that tolls are billed to the vehicle's owner based on license plate number, or transponder account. Be sure to check your rental agencies' policy regarding use of this road as some firms have been known to add fees and surcharges that can easily double or triple the original toll.
Many jurisdictions also have red light and speed cameras that issue fines via mail to the car's registered owner, again via license plate when the car is automatically photographed running disobeying a red traffic light or going above the speed limit. The above warning regarding rental agency policies applies to these as well. Your best bet to avoid this nasty surprise is to simply not run any red lights or speed.
By Ride Sharing
Ride sharing is increasing in Canada, as well as the United States, due in large part to the internet website Craigslist (http://www.craigslist.org) and dedicated ridesharing sites such as LiftSurfer (http://www.liftsurfer.com) and RideshareOnline (http://www.rideshareonline.com). This method of transport works best between major centres, for example Toronto-Montreal or Vancouver-Calgary. Generally anything along the Trans-Canada Highway corridor Victoria, Vancouver, Banff, Canmore, Calgary, Regina, Winnipeg, Thunder Bay, Sault Ste Marie, Sudbury, Toronto, Ottawa, Montreal, Quebec City, St Johns, Halifax, PEI should be no problem if your dates are flexible.
Some tourist destinations, especially those popular with young people, can be accessed via rideshare as well, for example: Vancouver-Whistler or Calgary-Banff. People sharing a ride will usually be expected to pay for their fair share of the fuel cost, and may also be asked to do some of the driving on long hauls.
For best results be sure to post a request listing, and start checking for offer listings at least one week prior to your anticipated ride date. Backpacker's hostel notice boards are also a good resource for ride sharing.
Like hitchhiking, some common sense and discretion is advisable.
By bus
Travel by intercity coach is available between most major cities in Canada. Service is best in the densely packed Windsor - Quebec City corridor which includes the major cities of Toronto and Montreal as well as the national capital, Ottawa. Service in this corridor is provided by a number of companies, chief among them being: Coach Canada (http://www.coachcanada.com) and Megabus (http://ca.megabus.com) whose main route is the heavily used Toronto - Montreal route, Greyhound (http://www.greyhound.ca/) who runs the Toronto - Ottawa route, the Montreal - Ottawa route and routes between Toronto and southwestern Ontario and Orleans Express (http://www.orleansexpress.com) who runs the Montreal - Quebec City route using modern, leather-upholstered coaches with North American and European electrical sockets at every seat. To the west of this corridor most routes are operated by Greyhound and to the east routes are operated by Acadian (http://www.smtbus.com/en/...) a subsidiary of Orleans Express. In Canada, only one company is given a license to run a particular route, as a result there is little to no competition among providers and fares can be unusually high and can be raised without notice. The only exception to this is the Toronto - Niagara Falls route, which is run by many American coach companies, who continue on to Buffalo and ultimately New York City. Prices on a U.S. bus company are usually slightly less than their Canadian counterparts.
Routes in the prairies can be extremely long, some of them taking several days; as a result, passengers should be sure they will be able to bear sitting in a seat for 48 or more hours with only rare stops for food and toilet breaks. Despite a recent violent murder on a bus in the prairies, intercity buses in Canada are generally very safe, however travelers should be aware of their belongings at all times and make sure that their valuables are on their person if they intend to sleep. In contrast to the United States, most Canadian bus stations are not owned or run by the coach companies serving them, they are generally run by the municipal government or, in the case of Montreal and Ottawa, a separate third-party corporation. Also unlike the United States, bus stations in Canada are not generally in the worst parts of the city, in fact, in Toronto, the bus station is located between a major theatre and shopping district and a neighbourhood full of large, wealthy, research-intensive hospitals.