The honest answer as to how often you should water your plants is: As often as they need it. I am being serious with that answer. There are so many things that determine how often you should water. (Plant size, life cycle, temperature, size of pot, medium growing in, etc). See what I mean. Depending on those and a few more factors will determine how often you "SHOULD" water. There is no formula, there is no chart.. A good rule of thumb may be to water every 3 days but if your plant is on the larger size and in a smaller bucket and it's hot and you are flowering, you will be watering every day. There are many factors to consider. This is what I think is easiest: get a good idea of what your plant feels like with no water in the pot (dry weight of plant and growing medium). Use that as your reference point. If the pot is very heavy than it is saturated with water and probably doesn't need watering for a bit. If it is light, approaching how the pot, plant and medium felt with no water, than it needs water.
As far as when to start using nutes, I start with mild nutes as soon as I start to veg.. Once the seedling has shown me the first set of leaves I start using mild nutrients.
PH range can change during the plant life cycle. With Coco, it is usually a lower PH range that is ideal than in soil but with either medium, optimal PH will really depend on the strain and where in the life cycle the plant is. Usually a good rule of thumb is 5.6 - 6.2 for Coco and a little higher for soil (say 6.0-6.5), but again that depends on strain and where the plant is in it's life cycle. Usually you will start the grow with a higher PH and slowly lower it a bit as you go further into flowering. This will increase the availability of the nutrients necessary for flowering a bit.
As to your last question about when to raise the nutrient concentrations, again it is like the first question, you have to listen to the plant. I bring up the level every time I feed until I get the first signs of nutrient burn and then I back it down from there. Again, this will also be somewhat strain specific. Good luck!!