Accept that plants are like people and they don't all need the same thing to be happy. So while it's great to set a day of the week that you plan to water your plants, be sure to always check the soil first. Some of your plants might be thirsty while others are fine to hold off. A good trick is to press your finger into the soil to the middle knuckle. If your finger is dry when you pull it out, water. If you have damp soil clinging to it, hold off.
A general rule: The thicker the leaves, the less water a plant needs. Succulents and cacti can store a good amount of water, making them low maintenance, while ferns, with their thin and lacy leaves, need almost constant moisture and higher humidity.
Humidity to plants is like body lotion or body oil to people. Without it, we get dry and flaky, especially in winter when we are running forced heat and the air lacks moisture. An inexpensive humidifier in the room near your plants works wonders, or you can zero in on those plants that need more humidity and set a tray or saucer beneath them with pebbles and water to add moisture directly to their environment. (Keep in mind the pot needs to have a drainage hole for this to work, or if you have enough room inside a solid pot between it and your growpot that can work too.) If not using a humidifier, mist the air around most plants at least weekly (with the exception of cacti and succulents).
Drainage is key. All plants need something to catch any runoff that they can't absorb, or else having 'wet feet,' i.e. roots constantly submerged in water, can lead to root rot and kill the plant. Best practice is to never direct plant a plant in a solid bottom pot, but instead, pot your plant one of two ways: directly planted into a pot with a drainage hole that's similar in size to the growpot it comes in or leave the plant in its growpot and drop it into a decorative exterior pot. If you choose the latter, just make sure you lift up the growpot and check after watering to make sure you aren't leaving standing water. Dump out any surplus water, and over time you'll start to get the hang of how much is needed.
Water every plant thoroughly. Giving your plant a little sip here and there is actually stressful for the plant. Instead, each time you water you want to continue until you start to see a bit of water run out the bottom of the pot. You also want to move the watering can around in a slow circular motion to make sure you're getting every bit of the rootball and not just in one spot. Remember, water moves down, not sideways!
Did you know that the number one killer of plants is actually OVERwatering and not UNDERwatering? Keep in mind that in winter, when days are shorter, your plants won't be photosynthesizing at their usual rate so they'll require less water. In spring and fall when the AC or heat kicks on, the air becomes drier and your plants might need a bit more water than usual until they adjust to the seasonal change.