Talk to your coach. Ask him what you need to do to shine throughout the others. Ask him what you need to improve on etc. Polish up the things that look rough. If you're trialed as a flanker, practice your reactions and ripping ball and collecting ball after tackles.
Search in Youtube for rugby fitness, also scrummaging techniques and that kind of stuff. In addition, be sure what position would you prefer as they have different roles, for example, props need to be strong in lower body but also in upper body, in contrast, the back row is known for having very powerful legs and stamina.
Ask your coach or look up some drills on 'Rugby world' magazine