Here are three different methods I use to get to and around Niagara Falls.
The WEGO Bus is a bus that takes you to many around Niagara Falls. The WEGO Bus makes stops at many of the main tourist attractions in the city and some of their stops are a walking distance from many nearby hotels.
You can get around the city by car and people who are visitors from other Canadian cities or crossing in from New York do, but you still should be prepared to walk since driving into the main tourist area is extremely busy and parking will be more difficult with other cars, pedestrians, and buses around. For our family, we parked the car at the hotel and mainly walked to get to the attractions and Horseshoe Falls.
If you are trying to get here from elsewhere in Ontario, you could take the GO Train as it stops at Niagara Falls Station. Keep in mind that the GO Train and Bus stops at the station are outside the main tourist section so you probably need to connect with the WEGO Bus or call for a taxi once you arrive.