No fear in changing tension settings if you take a picture. Don't pull your thread to test the tension if the pressure foot is up. When removing thread from the machine pull it off from the spool side rather then pulling out from the needle. Make sure when winding a bobbin to go through all the thread guide to get a properly loaded bobbin. A too tight or loose bobbin can cause problems. Discuss stacked threads and crosswise threads and how they should go on the machine to feed properly.