Seek out exercises that will help you develop a new musical vocabulary. Everything new that is learned will ultimately contribute to your ability to play well. Find regular settings in which you can play live with others. There's simply no substitute for this experience and it will make you a better musician. Never pass up a chance to play with great rhythm players.
Metronomes are great for timing and tempo practice.
For starters set it at a pace slower than you'd ever dream of playing. If you can't do it there, you won't be doing it any better at a faster pace. Allow yourself an occasional increase in speed, but never to the point of discomfort. Develop a practice schedule you can consistently maintain. Strive for a routine that consists of 10-15 minutes a day of thoughtful and controlled exercises or scales followed by some fun time.