Warming up is a huge factor for producing a good tone. In your practice session try this. Start off by taking out your tuning slide and just buzzing on the leadpipe on your F, concert Eb. Eventually try buzzing an F major scale descending into pedal tone range. Then spend awhile just doing long tones. Starting soft and slowly getting louder and then fade out as you run out of air. Then try slow lip slurs in all seven positions. Focus on tone more than anything throughout the entire warm-up. Focus on producing the best tone you possibly can. You'll be surprised about how your sound starts to open up. Also, like others have mentioned, start listening to players who have the tone you want. Listen to their sound and every time you play try focussing on getting your tone to sound like them. For me it's always been Chris Botti which brings me to my last point. Look into the Bill Adams trumpet method a bit. As far as tone goes, Bill Adams is the man. http://www.keynotesmagazine.com/article.php?uid=88 Best of luck with everything, trumpet will teach you just as much about life as anything.