I got a little water moisture meter at Lowes for $4, you stick it 2/3 the way down in your pot, and it has a scale of 1-4 with 1 being dry and 4 being wet. When it gets down to the 1-2 range I usually water, your pots will feel lighter too. If you have a couple seedlings, I would just check with your finger about an inch into the soil, and if it feels dry water it...someone else may tell you better I dunno