In the warmer months, Nizhny is a pleasant city to see on foot, and many of its attractions are within comfortable walking distance of each other; however, understanding its transport system is of course helpful when you're tired or don't feel like braving the rain.
Once in Nizhny Novgorod you will find the city centre is very walkable whilst public transport in Nizhny Novgorod (served by a network of metro, trams and buses) is very well developed.
Both buses and their smaller, shabbier cousins, marshrutki, cost 20Rbl per journey, which is usually paid (on avtobusi) to the conductor, who will come round and collect your fare, or (on marshrutki) to the driver. Make your way to the doors before your stop and press the buzzer above the door, or the driver might well not bother stopping.
Nizhny's buses are frequently crowded and less than luxurious, but thankfully there are a lot of them, so you'll not be waiting out in the cold long; besides, the homely feel of the marshrutki, complete with paisley carpet and tasselled wall-hangings is part of Nizhny's charm, and the satisfaction gained from successfully getting the right bus is worth the effort.
Nizhny is the home of (debatably) Russia's oldest tram system, and it shows: on parts of the track it's a distinctly bumpy ride. Nonetheless, Nizhny officials have refuted claims that the city's tramway is on the decline - 'Nizhny's tramway is alive!', in their words - and while not the most useful of transport systems, trams complement the city's architecture and provide a good way to see the city for new arrivals.
The Lower Town is home to the majority of Nizhny's metro system, working on a similar basis to Moscow's - buy a token at the 'kassa' just by the barriers.