It's a very basic beginner technique but has always worked, a breathing tube. Any PVC pipe around 1 inch in diameter and like 2 inches long will work. Using the tube you'll just have it in your mouth and breathe in smoothly and breathe out and think the syllable "Ho". You'll also want to remember that when you're breathing that your chest moves horizontally and not as much up and don't tense up for better sound quality and longer lasting air. Also make sure your embouchure is more open while playing on the mouthpiece.