hi, you will know when ur gecko is shedding when it starts to turn a pale/grey colour they'll also spend more time in their moist/wet hide. i'm fairly new to this aswell but this is wot i've noticed with mine hope this helped
He will get duller and duller in color and look dry. Mine took about 2 weeks to completely grey out and shed. Make sure you're providing a nice moist place for your leo to sit in to make his shed easier.
Here are several images to give you a better idea.
They start their shedding process from the moment they hatch. I believe they shed with in the first day or so of hatching then what every month-ish there after depending on growth. Some shed more than others some shed predictablly every 4 weeks some not. A lot is variable to each animal. Eros who is 7 mos old shed with in 2 weeks of me having him here.