While in college I took an internship at a flower arrangement shop that also kept a retail space filled with house plants. Most of my job was trimming flowers but I also did some upkeep for their inventory for the store. This was my first real experience trying to keep plants alive, before this I would buy plants, they would die a couple weeks/ months later and then I would buy another. So I had to learn a lot, and fast.
The first thing I learned was you can tell what you're doing incorrectly to a plant by what color their leaves are. For instance brown, crinkly dry leaves could be too much sun or too little water. Yellow leaves however mean you're watering too often.
Most of my personal houseplants have become little experiments, trying different combinations of care to see what yields the healthiest plant. I change up their location and watering schedule to see which they like the most. Also, I usually ask when I buy the plant what type of light and water they need but tweak their recommendations when I bring it home. The absolute biggest helper though, has been using a water bottle to mist the plants most days and watering them in the sink once a week.