Also, bach219, while using a tuner is helpful, you should keep it to a minimum and rely as much as you can on your ear to judge if you're in tune or not. If you can establish with the tuner which notes on your horn are off (usually sharp, but not always) then you can listen for that when you play and adjust as you go. That's what the loop connected to the third valve slide is for (to correct sharpness). Flat notes you'll have to blow sharp. Have fun and hopefully a great trumpet career.