I use the weight method. Pick the pot up and if it feels light water it just a little. Small seedlings will grow better when the soil is slightly moist, and not cold. Make those roots grow and let them seek the water for themselves and do their job. Use a set of scales and measure weight when first potted because fresh bagged soil is moist enough for growth. Water the top until you get a little run off from the bottom and then leave it under the light for heat. Weigh it every few days until the weight returns to roundabout the original and water again and repeat for a few weeks.