Practicing is good advice but only goes so far. People have a tendency to practice what they know so they stay the same. Here are some ways to break the cycle:
1. Take songs you already know, especially songs where you know a fingerpicking arrangement, figure out how to play them in more than one key.
2. When you play with a uke jam, or play familiar songs, use chords in a different position up the neck.
3. Take a break from uke for a couple of months (this is counterintuitive, but studies have shown that it takes a while for skills to get hardwired into the brain). I've found that if I take a break I lose a little, but after a couple of weeks improve more than I ever could before.
4. Learn music theory and learn how to read music
5. Get a keyboard (I use a cheap $40 Casio). Train your ear. Learn how to recognize what you hear, translate it into music and then translate it into the ukulele.
6. Learning techniques and scales, etc will only take you so far. Learn to hear music,really hear it, then to play what you hear.
Jake Shimabukuro, Daniel Ho, Britney Paiva, Sara Maisel, Jason Arimoto, James Hill, Gerald Ross - they are all musicians. If you want to go to the next level, learn to play music on the ukulele, don't just focus on learning the ukulele.