LISTEN! - That's it.

It's really just that simple.
Listen to everything! Listen to all kinds of music and listen to what everyone in the ensemble is playing. Listen to classical and jazz and pop and rock music. Listen to the melody and the rhythm and the harmonic structures. Listen to the spaces between the notes. The space between the notes is as important as the notes, sometimes, even MORE important than the notes.

Listen to how the instruments in different styles integrate with each other. Is the bass coming in slightly before or slightly after the drummer? Are the bass and drums locked together? Is the kick drum locked note for note with the bass part or just hitting the accents for the bass part? How does the guitar part fit with what the bass and drums are playing? How are the drum fills complimenting the melody and rhythm of the song?

How does the percussion section of the symphony differ from the percussion part of a jazz band or a rock band? Can you play a symphonic sounding drum part in a rock song?

Now Listen to what everybody in your own band is doing. Are you playing with them or just playing a bunch of your favorite licks? Are you being a drummer or just keeping time like a metronome?

Practicing various exercises to build your technique is great for developing TECHNIQUE, but technique alone is NOT musicality! Technique is simply the means to expressing the music.

Knowing the alphabet is not enough to be a great writer, to become a great writer one must read and write. Read everything and then start writing once you have something to say and keep writing. It is the same with music. Your musical technique/chops are like knowing the alphabet. Listening to the music that has been made before is like reading. And writing music is like writing words. You really should have something to say before you start talking.

Listening to a wide variety of music, really listening to all the intricate details of the various kinds of music, will help you develop something interesting to say.

Practice "listening" every day!