Seedlings don't use much water at all. When you water, do it thoroughly, til it runs out the container holes, then I drain mine on an angle, also very thoroughly.
Don't water a little bit at a time. This causes problems.
Feel the weight of the pot after it's drained. When it needs water, it'll be much lighter.
Much better to under water than to over water.
Learn to water by need, not by schedule. Things change and water needs depends on these changes.