If I could like the post
@Ablaze made multiple times I would.. lol. Going by the weight of the pot works well, but I like to watch the top of the soil. When the top 1.5-2" of soil get bone dry I water.
And the amount is both dependent on the size of the plant and the type of medium. In organics I like to water when the top inch of dirt is dry, and not with too much runoff. But every 1.5-2weeks MIR (make it rain), simulate a nice thunderstorm, lots of runoff, and then let her dry out a bit more before the next light watering. Gotta keep it fresh. typically you want to see some runoff when you water, especially in soiless mediums or any other time you're using synthetic nutrients. For instance, in coco I use DG foliage pro, and add it 1/4-1-2 strength almost every watering depending on how hungry or not hungry she looks. And I aim for a decent quart or so of runoff to flush out any excess salts.
Not all plants are happy with the balance of nutrients in liquid fertilizers. Thus when they chill for several days in the nutrient water I gave them at the last watering they might have eaten up all the nitrogen and potassium I gave them, but they weren't really hungry for phosphorus. So next time they get water, they get enough to flush out some of the P (or any of the other plethora of nutrient salts they didn't take in).
When you grow indoors, you're playing god. Think like mother nature. MIR.