Most importantly, make sure that your newly potted seedlings will be in constant sun or under a grow light during the day, that they are watered regularly, but not over watered, and that they will be warm enough. Tomatoes need 75 degrees during the day to grow. 85 degrees is their favorite temperature. The difference creates greatly different results. Turning your pots a quarter turn daily will assure even growth, but is not essential in a greenhouse. In your house, turning the pots is very important.
A hint or two on transplanting. Take your time. Be gentle. Put a little soil in the bottom of the 4" pot, and then place the peat pellet in the pot. While holding the seedling stem gently, place more soil around it to support it. Then fill it almost to the pot's rim, leaving a little room for water to pond on the top before it sinks in, so it doesn't run out of the pot.