There is no life without water. True for watercolour painting too!
The first, and most common, is; how much water should I use when mixing watercolour paint? To answer this one question I must ask you to answer the following six:-...
What tone (lightness or darkness) are you are trying to achieve? A light tone requires more water than paint and a dark tone requires more paint than water.
Do you have your board tilted at an angle? The steeper the angle the less water is needed to allow the paint to flow down the paper. The image below is from my video Painting a Flat Wash in which you can see from the dark area just how watery my washes are when I paint large areas.
Finally, all of the above relate to one another, and that is what makes painting in watercolour a skill (that can be learnt): Practice makes perfect.
*This artist enjoys watching both water and paint dry!