So back in the days when I was a piano student I learned about the "anacrusis" principle for good phrasing in music. This principle, as I understand it, was taught to students back in the 1800's, but seems to have gotten a bit lost from teaching, since I never heard of it from my own teachers. There is a lot to say about this, in my opinion, highly valuable little principle, but I'll keep it brief.
Basically music is made up of notes on the beat and off the beat. A tool for intellectually understanding how to play a phrase with direction is to consider all the notes off the beat (between the beats) as aiming towards the next beat. For example, in the opening of Beethoven's fifth symphony, we have the da-da-da-DUUUUM, where the three quick notes "aim" towards the strong DUUUM on the beat. Likewise, when we construct a phrase, we play the notes in between the beats to aim towards the next beat.
Learning about this principle was a revelation to me back in the days. I was sometimes criticized for my phrasing lacking direction or sounding clumsy, and I could sort of hear it, but wasn't sure what I needed to change to improve matters. Part of the problem was that I was accenting the beats and then the notes between the beats where just kind of there, without providing any sense of propulsion towards the next beat. This resulted in a kind of angular, heavy, mechanical sounding phrasing.
What are some principles y'all have found helpful for phrasing that you keep in your musical toolbox?