If you're a train buff, it's possible to get there by train - see
VIA Rail Canada, C$21 each way. The train actually runs between Toronto and New York, and you should be aware that long-distance passenger trains in North America often run many hours late! The rail station is a couple of miles from the falls, so you'll probably want a taxi too. Toronto's Union Station is an impressive building in its own right.
There are a myriad tour bus companies that will take you to Niagara Falls with a variety of more or less inclusive packages.
As you will be there in the Fall, if you want to see some of the glorious foliage colours, you could do worse than take a day trip on the
Northlander (Ontario Northland Railway). But I'm sure there are some locals who visit this forum and can give you far better advice than I.