You'll get to know a plants life cycle once you get a few grows under your belt
and thats for any plant, really!
As Alpha said, perky and green is good. New growth is good. A happy plant will do its best to grow, and reach towards that light!
Dry and crispy most likely means too many nutrients were fed. That, or it can also be drying out.
Sad and droopy most likely means too much water. It can also mean not enough water though, just have to judge the situation as best you can.
Taco/curled leaves can also come from those situations, and can even happen when you have too much airflow. Leaves will 'sweat', and are cool to the touch most of the time. If you blow that moisture away too fast it can make your leaves curl a bit.
When you train your girls they may not grow much for a few days or a week or so. This is called 'stunting', and its mainly your girl repairing the damage you did during the training session before she gets back on track!
Theres a lot more to growing but just watch your girl and she will tell you all you need
Just be sure not to kill her with too much love! Remember that its a plant, and that nature will take its course so long as you give it what it needs! Good luck.