The Metronome is your best friend
It's there for you more than your girlfriend, feel down? Get up by uping the tempo!!!!!!
I have just recently noticed how well this thing will help you with a certain packet that has very hard Jazz stuff to play. It consists of odd measures, weird beats, off beats, the whole nine yards.
This thing will help you with everything in this, from really slow where you need to sight-read level, to mind blistering fast bebop lines:
Just by re-looking over with this exact metronome, I noticed bad things that I can work on instrantly, giving me an advantage as soon as I applied this work. With the great measure counter, you can be 99% sure that you are playing withing the measure and not "guitar/4" or whatever you'd like to call it.
What I simply mean is that getting a metronome will get your foot in the door for many things, especially for attacking those hard-to-count licks...