Practice playing your instrument in the dark. This will force you to feel the positions of your hands and will teach you to listen to the sounds you are making.

Where possible, play along with someone else. This can stimulate you to try new tunes or new styles.

Teach someone what you know. If an opportunity presents itself, share what you have learned with someone who shows an interest. Remember that they would not ask you unless they thought you knew something worth sharing. Often teaching will help you to solidify what you have learned. It can also cause you to examine aspects you had never before considered.

When singing, try to hear the meaning of the lyrics and to impart that to the manner in which you present the song. It is one thing simply to read a poem aloud and another to portray the feeling of it. Experiment with increasing or decreasing volume. Exaggerate the emotions the words invoke. Be theatrical/histrionic when practicing. Then tone it down a little, (if need be,) when performing.

Practice.