That's the tricky part especially with Jiffy pots, which I personally hate. The trouble with the peat pots is they hold moisture in so the soil tends to stay too wet, but if the soil starts to dry out at all then they suck all the moisture out for themselves and make it too dry, but the pot is still moist and gets moldy. Oh well. What you are aiming for as I said originally is for the soil to stay a little bit moist but not wet. With my plastic pots, I set them in a tray and put a little water in the tray and let the soil suck it up. Doesn't work as well with Jiffy pots, because the pot sucks it up instead, but you could try it. Otherwise, if you are watering from the top, I would put a little bit of water in very gently until a few drops start coming out the bottom. Then leave it alone until the surface just starts to dry out (barely). That should work out to about once a day, but depends a lot on conditions.
BTW when it comes time to transplant your little plants into the ground, DO NOT plant them in the Jiffy pots; peel the pot off. Despite what they say, the pots do not break down in any reasonable time and tend to strangle the plant and continue doing the too wet or too dry routine.