Trombone Lessons: Introduction & Basics 

Ramón Ricardo Pérez me too.-.

work on your breath attack

nearly all non f trigger tenor trombones are small bore, as most f trigger tenor trombones are large bore, (and also just because a trombone doesn't have an f trigger doesn't mean its a beginner trombone, small bore trombones without triggers are common in jazz, and blues, and many people use them in marching bands).

andante et allegro J (Joseph) Guy Roparts

Depends on what you want: easy high notes, easy low notes, dark sound? In my opinion, a good all around mouthpiece is a Bach 7 mouthpiece. I suggest you look at Bach's mouthpiece guide to learn about what the different mouthpiece constructions do, then decide for yourself. Look at other manufacturers, too. Yamaha has really good pieces and so does Schilke. Also, after you can comfortably hit a D above the staff, ditch the 12C, and if don't have one, stay away from them.