One Octave Scale and Patterns
The majority of fiddle tunes are based on a major scale, some being more minor scale oriented. Knowing scales well helps build strength, dexterity and fretboard knowledge, and all of those things are important when navigating a new fiddle tune.
Take your time when playing through these scales. You want to play fast I know, but if you will sound sloppy if you move too quickly before you are ready. Take your time. The longer you hold a finger down, the more those muscles in your hand and digits are engaged. This is how you build strength and good muscle memory.
Play just behind the fret to get a good tone. Right on or too far back will cause muted or buzzing notes. Remember to leave fingers down when possible and not to fully open your hand, keep the fingers in a low and relaxed curl over the fretboard when not in use.