Brave, well a lot of it is just feel, something you develop with time and experience with your exact setup and since there are so many variables it's hard to give detailed advice. That said, I don't let them dry out too much, although in the early stages it's always better to err a bit on the dry side since over-watering is certainly one of the main bugaboos of this hobby. We fuss and tend to them too much and end up killing them with kindness, lol.
In the early stages, since their roots haven't reached the reservoir at the bottom, you only need light waterings - how often depends on the ratio of your mixture, temps and ambient humidity. If you're uncertain about the moisture content, just poke your finger down into the medium about a couple of inches to see if it feels moist, but once you feel confident that the root system has reached the res, then space out feedings (3-4 days say) and when you do feed, make sure to add enough so that you get a little overflow, 10-15% say, so you keep it fresh (if you never water to overflowing then nutrient salts could build up and cause you some issues).
As your grow progresses, try to get an idea of what your buckets weigh right after a feeding and then again when they're definitely in need of water. Also dependent upon the strain, and especially if you have a fair amount of soil added to the mix, you can alternate between feeding nutes one time and then watering the next, adjusting nute strength if you begin to get nute burn, or simply watering twice say to every feeding. You just have to find out how to dial in your system, and that's probably going to take a few grows before you get it where you know where that sweet spot is.
I admit that I try to push my girls to the max (after they've gotten well started) and then back off and watch for nute burn like a hawk. I'm convinced that serious nute burn can stunt growth or at least slow development, and when I see nute burn I will flush with water, make adjustments to the nute strength, and then I cut off the damaged tips of any leaves so that next time I check it's easier to identify new damage from old.
Btw, this works best when you run the same strain several times, but if you're like a lot of folks, they end up growing different strains every grow making it harder because you won't know if a problem is specific to your system or if it's the strain(s) you're growing (been there, done that ;?). Patience and an eye for detail are crucial, and taking notes helps you to recognize patterns as well. That's it in a nutshell, follow my advice and you'll be an expert in no time.... just kidding, you can do this hobby half your life and you'll find there's still things to learn dude, but good luck and grow well ;?)
