Keep your trombone in immaculate condition. Ask someone to demonstrate the correct method for cleaning and lubricating the slide. Avoid using oil. Instead use Slide-O-Mix. Then use a spray bottle to create beads of water on the inner slide each time you play. Clean the slide frequently and guard it with your life. Most accidents are caused at the conclusion of a rehearsal when someone else bumps your instrument. Always take your time when assembling and disassembling the instrument. If there are bumps in the slide, see the repairman today. Most tuning problems and legato style problems are caused by slides that cannot be manipulated easily.