How to water indoor plants?

There is no specific frequency that works for all plants, instead what you should do is determine what kind of plant you have and follow guidelines on how often to water it by doing research, there is  no thumb of rule which could apply for watering as different type of plants have their own requirements. We can try to make out some basic rules to understand common behaviors.

Water your plant if the soil becomes lighter in color or cracked.
Plants in the succulent family require periods of dryness between watering, if you notice standing water in or under the the pot, empty it out, so that plant is not sitting in it, standing water can kill plants. Plants with lush or thick leaves require more water than plants with waxy or leathery leaves, if soil is dry or over watered it can damage plant roots and prevent plant from growing in both conditions.

Stick your finger in the soil to determine how wet it is below the surface.
If you poke your finger into the soil up to your knuckle, you can feel if your plant needs more water. If the soil feels damp, then you don’t need to water it. If it feels dry then it’s likely you need to water it. Again, this varies from plant to plant. These conditions will work for most plants but not all of them. Signs of over-hydration include discolored leaves, lack of leaf growth, loss of leaves, and soft rotten patches. Signs of dehydration include slow leaf growth, brown and dried leaf edges, and lower leaves becoming yellow and curled.

Use water that is at room temperature.
20° C is the best temperature to keep the water that you’re using to water your plants. You can use a thermometer to determine the temperature of the water, or you can leave the water out, after you pour it, and allow it to become room temperature. If your water is too hot it can cause roots damage, potentially killing your indoor plant. Water that is too cold causes dormancy in your plant, which will stifle any existing and future vegetation.

Select a pot that has good drainage.
Amount of drainage in the pot you’re keeping your plant in is very important because over or under watering your plant can damage or kill it. Make sure that there are drainage holes at the bottom of your pot. Materials like plastic, metal, and glass will absorb much less water than ceramic or clay, keep this in mind as well. Make sure that there are holes at the bottom of pot so that water can drain. If you are using a cachepot (which has no holes), water can build up and kill your plant.

Reference : https://www.wikihow.com/Care-for-Indoor-Plants