I'll be the first to admit that figuring out how much you should water your plants can be daunting ("WHY ARE YOU TURNING YELLOW???" —me screaming at my new succulent), but it doesn't have to be this way. Your plants will straight-up tell you whether or not you're giving them enough hydration: You just have to look out for the signs.
It's over-watered if:
• The leaves' tips are turning brown
• The stem's base is soft and mushy
• Yellow leaves are falling off throughout
It's under-watered if:
• The leaves are starting to curl
• The leaves' edges are brown and crispy
• The lower leaves are doing the worst
So, what now? If your plant is under-watered — you guessed it — give it some water, and do so a bit more frequently than you were before. Don't worry about sticking to a set schedule though — it's better to be flexible and stick with this general rule of (green) thumb: Only water your plant when the top two inches of soil feel dry. Also, use warm water instead of cold, as the soil absorbs it more easily.
If your plant is over-watered, you should gently remove it from the soil, cut off any rotten roots, and, after letting it dry out for an hour or two, repot it in a pot with better drainage. Go for one with a drainage hole and tray (terra cotta is ideal), or, if it doesn't have a hole, add some lava rocks to the bottom, which will soak up any excess water.