Like most of those popular Central-South American tropicals, Maranta prefers bright but indirect light. Being a part of the forest undergrowth, the species hasn’t evolved to be able to deal with strong direct sun.
This species is not used to lower temperatures and will likely stop growing or even begin shedding leaves if you let things drop below 60°F. Keeping it at room temperature is a much better idea, although higher temps aren’t much of a problem either.
Your Maranta will appreciate being kept lightly moist. “Lightly” means it feels slightly damp, but absolutely never soppy. It’s fine if the top inch or two of the soil dries a little, at which point you can give the plant a sip.
The other main issue with Maranta is also related to moisture, but in this case, the levels in the air. Jungle habitats like the ones that prayer plants naturally grow in are often at 100 percent air humidity (!), meaning that this species isn’t really used to the much drier air in our homes.
It can be very helpful to get a cheap humidity meter (like this digital hygrometer that I love and use) so you can keep an eye on things. If it consistently gives you readings under 50 percent, your houseplants (almost all of them, not just your Maranta!) will probably benefit from the use of a humidifier nearby.