First and foremost, figure out your exposure. Do you see the sun come up in the morning through your window? You have eastern exposure. Do you see the sun set through your window? That's western exposure. Does the sun move past your window left to right? Southern exposure. Right to left? Northern exposure. (Keep in mind that things like buildings or trees blocking light or heavy curtains can affect this exposure, but at least you know which direction you're facing.)
Eastern: Bright but not harsh and will support most plants, particularly those classified as medium light.
Western: Bright but harsher/hotter in afternoon, so avoid sensitive low-light plants like ferns and embrace high-light plants such as succulents and cacti.
Southern: Typically as close to full sun as it gets, making it a great room for most any type of plant. Just keep an eye on where the sun's rays hit in the room and adjust accordingly, as many plants' leaves can burn if in direct sun.
Northern: Getting the least light of the bunch, this exposure is best for low-light plants like sansevieria, philodendron, pothos, ZZ and some ferns.
If you've been cursed with a low-light or no-light home and you'd still like to green it up, supplemental lighting is the answer. There are countless solutions on the market, but for starters, just know that incandescent bulbs should not be used. They emit heat and only offer red waves of light, not the blue waves needed for healthy leaves. LED lights are more expensive up front than fluorescent, but they're much more efficient in the long run. Plus, advancements in LEDs also means you can get both the red waves (needed for blooming plants) and the blue waves (for foliage health) combined into a light that's white in appearance, instead of that glowing fuchsia color tone of the past.