When practicing synchronization of the hands, it is important to remember to begin with a slow tempo and to use a metronome. I know not everyone enjoys practicing with a metronome, but it really is the most efficient way to practice the technical aspects of music. You'll want to use guitar exercises that are very easy and effortless for you to play. This will allow your attention to be focused on whether or not your hands are in sync rather than worrying about playing the exercise correctly. As you play through your exercise of choice, pay close attention to the sound of the notes you are playing. Listen for muted notes or unintentional rests between the notes as this will be an indication that your hands are out of sync. Once you can play the exercise cleanly and smoothly, you should begin to increase the tempo of the metronome. Ultimately the goal should be the ability to play clean passages at any tempo. The real challenge of synchronization, as with many other guitar techniques, will be to play clean sounding notes at blazing fast tempos. Remember to pay close attention to the sound of each and every note you play and set reasonable goals for your skill level. As your synchronization improves, you will be amazed at how much less effort you have to put into those difficult and fast passages.