i used to advocate the sticking your finger in the dirt and feel method, but i was stupid. lol, their is an easy way-(step 1 can probally be skipped but it might make it easier on you to tell the first few times till you get the hang of it.)1.- find a pot the size of the one youve got your plants in. 1.5-fill it with soil- pack it in their a little bit, but not too much. step 2. lift your pot up and compare the weights of the 2. also make a mental note on how heavy the pot feels after a good watering.hope this made sense, im kinda rambling on, lol, its easy when you get the hang of it.