I think everyone has their own rules on when and how much water, I tend to sow in quite dryish compost, then stand the trays in water until the tops are wet, then don't really water again until the babies start popping though, unless of course the compost dries, then I water with a watering can, cos I am tooo lazy to then carry all the seed trays back into the house to water at the sink! The way I understand it is too much water is as bad as too little. See, something else to catch us out and trip us up!