Timing is one of the most important factors of playing music. Without precise timing your music lacks energy and clarity.
One essential thing you need for practicing your timing is a metronome. Metronomes come in all kinds and shapes. I've used a model like this for 15 years now (my mum gave it to me as a Christmas gift). There are also digital ones like this Seiko metronome.
For this timing exercise we need:
1. Warming up exercise: set the metronome at 150 and play the theme. When you can play it without mistakes and tension in your fingers and arms, drive up the speed by 5. Continue to do this until you're at a speed that's not comfortable for you to play anymore. Do this everyday and you'll see a huge improvement in your guitar technique.
2. Set the metronome speed to 80. Now the clicks of the metronome are the first and the third beat of a bar, so we're actually playing at a speed of 160. Have a look at the tablature:
3. Let's make the feel a bit more jazzy: metronome still at 80, but now the clicks are the 2nd and the 4th beat of a bar:
This is a bit more difficult, especially with anticipations like the 4th beat of the first bar.
4. Now set the tempo to 50. Every click is the 1 of a bar, so we're actually playing at a tempo of 200. This is not very easy, first try to find the beats in your head before you attempt playing your guitar.
5. Let's make it even more difficult: every click of the metronome is the 2nd beat of a bar:
6. Every click is the 3rd beat:
7. Every click is the 4th beat (this is hard):
Try this with different themes and gradually increase the tempo. Freaks can try this exercise: every click is the second quaver of the first, second, third or fourth beat.