This kind of thing is key - make it easy to use transit and lower the marginal cost of doing so. Yearly subscriptions are good. London's approach—unify almost all modes under the same payment system with automatically calculated caps and discounts—also works quite well as you don't have to think about buying passes, individual tickets, etc. Just tap and go and the system takes care of it for you.
Not many places in the US have this level of integration yet. For instance, the NYC Ferry, NYC Subway, LIRR, Metro North, PATH, and regional Amtrak service all use disjoint ticketing methods. It'll slowly get integrated over the next decade, but it greatly increases the mental effort needed to hop on transit. Perhaps the closest in the US is the Bay Area's Clipper Card - they managed to shoehorn over a dozen area agencies onto the same payment method - but it's still not quite as good as something like London's Oyster.