Contact points with the bike (feet, hands, bum) need the same considerations as an outdoor bike especially if you intend to be on there for hours at a time. Gears also need some consideration, if you're content to just cycle flat loops then this is less important but if you intend to attack some of the steep parts on Zwift (Pretzel, Alpe du Zwift etc) then you'll probably be in need of some Granny gears
A training tyre for a wheel-on type trainer is
in my view worthwhile but opinions differ hugely on this point. Keep the pressure in the tyre maintained (assuming wheel-on type trainer again), this is especially important for turbo trainers with small diameter rollers.
As others have said - fans, lots of them! and remember to hydrate, you'd be surprised how easy it is to dehydrate on a trainer. With insufficient ventilation you'll overheat quickly and with lots of ventilation your sweat will evaporate rapidly (if I forget to open a window in my Zwift room the glass becomes steamed up in no time :O )