Most of the guidelines people use are based around EC/PPM. For example the most common starting point is 0.8EC for seedlings. But after that point, like Skatter said, it's all about reading the plant and its needs so you know when to up the feed and vice versa. For a perfect completely unhindered grow on average you would increase EC by 0.2 each week but all plants have a preference you'll just have to watch her closely. It's tricky at first and remains tricky but I'm starting to get the hang of it now during my second attempt at DWC. I wish you the best of the luck and the best advice I can give you is to literally demolish the forum for all the info you could possibly need, read journals by Komach, DWCocha, Seymour Buds and myself (a good show of how to mess things up and recover) amongst others and you will feel a lot more confident. Its how I learned and I'm sure a lot of others too. 


Could always start a "good v bad coco" thread in the coco section ?